Niraparib plus abiraterone acetate with prednisone in patients with metastatic castration-resistant prostate cancer and homologous recombination repair gene alterations: second interim analysis of the randomized phase III MAGNITUDE trial

BACKGROUND

Patients with metastatic castration-resistant prostate cancer (mCRPC) and BRCA alterations have poor outcomes. MAGNITUDE found patients with homologous recombination repair gene alterations (HRR+), particularly BRCA1/2, benefit from first-line therapy with niraparib plus abiraterone acetate and prednisone (AAP). Here we report longer follow-up from the second prespecified interim analysis (IA2).

PATIENTS AND METHODS

Patients with mCRPC were prospectively identified as HRR+ with/without BRCA1/2 alterations and randomized 1 : 1 to niraparib (200 mg orally) plus AAP (1000 mg/10 mg orally) or placebo plus AAP. At IA2, secondary endpoints [time to symptomatic progression, time to initiation of cytotoxic chemotherapy, overall survival (OS)] were assessed.

RESULTS

Overall, 212 HRR+ patients received niraparib plus AAP (BRCA1/2 subgroup, n = 113). At IA2 with 24.8 months of median follow-up in the BRCA1/2 subgroup, niraparib plus AAP significantly prolonged radiographic progression-free survival {rPFS; blinded independent central review; median rPFS 19.5 versus 10.9 months; hazard ratio (HR) = 0.55 [95% confidence interval (CI) 0.39-0.78]; nominal P = 0.0007} consistent with the first prespecified interim analysis. rPFS was also prolonged in the total HRR+ population [HR = 0.76 (95% CI 0.60-0.97); nominal P = 0.0280; median follow-up 26.8 months]. Improvements in time to symptomatic progression and time to initiation of cytotoxic chemotherapy were observed with niraparib plus AAP. In the BRCA1/2 subgroup, the analysis of OS with niraparib plus AAP demonstrated an HR of 0.88 (95% CI 0.58-1.34; nominal P = 0.5505); the prespecified inverse probability censoring weighting analysis of OS, accounting for imbalances in subsequent use of poly adenosine diphosphate-ribose polymerase inhibitors and other life-prolonging therapies, demonstrated an HR of 0.54 (95% CI 0.33-0.90; nominal P = 0.0181). No new safety signals were observed.

CONCLUSIONS

MAGNITUDE, enrolling the largest BRCA1/2 cohort in first-line mCRPC to date, demonstrated improved rPFS and other clinically relevant outcomes with niraparib plus AAP in patients with BRCA1/2-altered mCRPC, emphasizing the importance of identifying this molecular subset of patients.

Oral EPI-7386 in patients with metastatic castration-resistant prostate cancer

177

Background: EPI-7386 is a next generation aniten, a novel class of compounds designed to inhibit androgen receptor (AR) activity by binding to the N-terminal domain. Preclinical data supports disruption of AR regulated gene transcription even in the presence of resistance mechanisms including ligand-binding domain point mutations and truncated splice variants. Here we report results of the Part 1a first-in-human trial of EPI-7386 in mCRPC (NCT04421222). Methods: This Phase 1, open-label, multicenter, dose escalation (Part 1a) and expansion (Part 1b) trial was designed to evaluate the safety, pharmacokinetics, pharmacodynamics, and antitumor activity of EPI-7386 in mCRPC patients (pts) progressing on standard of care treatment, including next generation antiandrogen(s) and chemotherapy. Originally designed to assess up to 5 doses of EPI-7386 (200, 400, 600, 800, and 1000 mg QD), two additional cohorts were added examining 400 and 600 mg BID due to 600 mg QD showing exposure saturation while demonstrating a favorable safety profile. Results: 31 pts were enrolled in the QD cohorts and 8 in the BID cohorts. Pts had a median of 4 lines of prior therapy for mCRPC: 83% received abiraterone and at least one next generation AR inhibitor, and 58% had at least one line of prior chemotherapy. No DLTs were observed; EPI-7386 was safe and well tolerated at all doses/schedules evaluated. All related adverse events (AEs) were Grade 1 and 2 and consistent with AEs associated with second-generation antiandrogens. For doses above 400 mg QD, exposures were at or above those associated with antitumor activity in animal models. Evidence of antitumor activity (including significant and durable PSA responses and/or decreases in ctDNA, and/or radiographically documented tumor shrinkage) were observed in pts with fewer than 3 lines of treatment for mCRPC, no visceral metastases and no prior chemotherapy (9/31 pts). Conclusions: Part 1a treatment with EPI-7386 monotherapy was safe, well tolerated up to a daily dose of 1200 mg (600 mg BID), achieved target clinical exposures and showed preliminary signals of antitumor activity in heavily-pretreated mCRPC. Part 1b is open with enrollment focused on pre-chemotherapy, post-second generation antiandrogen treated mCRPC pts in one cohort, and treatment-naïve non-mCRPC pts in a window of opportunity proof-of-concept second cohort. Two doses will be evaluated (600 mg BID and QD) based on FDA Project Optimus recommendations. Clinical trial information: NCT04421222 .

Impact of run-in treatment with abiraterone acetate and prednisone (AAP) in the MAGNITUDE study of niraparib (NIRA) and AAP in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) and homologous recombination repair (HRR) gene alterations

172

Background: NIRA/AAP significantly improved outcomes in pts with mCRPC and HRR gene alterations, particularly in BRCA, in the phase 3 MAGNITUDE study. As a practical measure, pts were permitted to receive up to 4 mos of AAP (in 1L mCRPC) prior to randomization to allow time for genomic testing. We evaluated the impact of AAP run-in treatment on the efficacy of NIRA/AAP. Methods: 423 pts with mCRPC and HRR gene alterations were randomized 1:1 to receive NIRA/AAP or placebo (PBO)/AAP. At the prespecified second interim analysis, a sensitivity analysis based on the duration of AAP run-in was conducted. Pts with BRCA alterations were also analyzed separately. Results: Median duration of prior AAP treatment received was 1.9 (range, 0.3–4.1) mos. Pts receiving AAP ≤2 mos had similar benefit (radiographic progression-free survival [rPFS] hazard ratio [HR], 0.69 [95% confidence interval [CI], 0.36-1.30]; time to cytotoxic chemotherapy [TCC] HR, 0.52 [95% CI, 0.24-1.11]; time to symptomatic progression [TSP] HR, 0.32 [95% CI, 0.13-0.79]; Table) to pts not receiving any prior AAP. rPFS benefit was not demonstrated in pts who had previously received AAP >2 – 4 mos: HR, 1.47 (95% CI, 0.66-3.30). Findings were consistent in the BRCA population. Conclusions: Pts receiving a short run-in (≤2 mos) of AAP alone obtained similar benefit from NIRA/AAP as those who received both NIRA/AAP together for initial treatment of mCRPC. While interpretation of data is limited by the small sample size and event numbers, for pts where NIRA/AAP is being considered as therapy, AAP may be initiated during HRR testing and combination treatment should be initiated expeditiously once HRR positivity is established to attain maximal treatment benefit. Clinical trial information: NCT03748641 . [Table: see text]

Efficacy and safety of darolutamide (DARO) in combination with androgen-deprivation therapy (ADT) and docetaxel (DOC) by disease volume and disease risk in the phase 3 ARASENS study

15

Background: In ARASENS (NCT02799602), DARO plus ADT and DOC significantly reduced the risk of death by 32.5% (HR 0.68; 95% CI: 0.57–0.80; P<0.0001) vs placebo (PBO) + ADT + DOC in patients (pts) with metastatic hormone-sensitive prostate cancer (mHSPC), with similar overall incidences of treatment-emergent adverse events (TEAEs) between groups. The effect of DARO on overall survival (OS) was consistent across prespecified subgroups, including de novo and recurrent disease. For pts with mHSPC, outcomes based on disease volume and risk provide additional information to clinicians. Methods: Pts with mHSPC were randomized 1:1 to DARO 600 mg twice daily or PBO, with ADT + DOC. High-volume disease was defined as visceral metastases and/or ≥4 bone metastases with ≥1 beyond the vertebral column/pelvis (CHAARTED criteria). High-risk disease was defined as ≥2 risk factors: Gleason score ≥8, ≥3 bone lesions, and presence of measurable visceral metastasis (LATITUDE criteria). OS for these subgroups was assessed using an unstratified Cox regression model. Results: Of 1305 pts in the full analysis set, 1005 (77%) had high-volume disease, 912 (70%) had high-risk disease, 300 (23%) had low-volume disease, and 393 (30%) had low-risk disease. DARO + ADT + DOC prolonged OS regardless of high- or low-volume disease with HRs of 0.69 and 0.68 vs PBO + DOC + ADT, respectively. OS benefit of DARO vs PBO was also similar for pts with high- or low-risk disease. DARO improved clinically relevant secondary endpoints vs PBO in high/low-volume and risk subgroups, with HRs generally in the range of those observed in the overall population. Incidences of TEAEs were consistent with the overall ARASENS population across subgroups by high/low volume and high/low risk. Conclusions: In pts with mHSPC, the benefits of early treatment intensification with DARO + ADT + DOC on OS and key pt-relevant secondary efficacy endpoints vs PBO + ADT + DOC were similar in patients with high- and low-volume as well as high- and low-risk mH+SPC. The favorable safety profile of DARO was reconfirmed in high/low-volume and high/low-risk populations. DARO + ADT + DOC sets a new standard of care for pts with mHSPC. Clinical trial information: NCT02799602 . [Table: see text]

Dosing, safety, and pharmacokinetics (PK) of combination therapy with darolutamide (DARO), androgen-deprivation therapy (ADT), and docetaxel (DOC) in patients with metastatic hormone-sensitive prostate cancer (mHSPC) in the ARASENS study

148

Background: In ARASENS (NCT02799602), DARO in combination with ADT and DOC significantly reduced the risk of death by 32.5% (HR 0.68; 95% CI 0.57–0.80; P<0.001) vs placebo (PBO) + ADT + DOC in patients with mHSPC. Incidences of treatment-emergent adverse events (TEAEs) were similar between treatment groups. We report dosing, safety, and PK of coadministration of DARO and DOC with ADT. Methods: Patients with mHSPC were randomized 1:1 to DARO 600 mg twice daily or PBO, plus ADT and DOC (75 mg/m2 q21d for 6 cycles). The effect of DARO on DOC PK was assessed by noncompartmental analysis from the first 25 patients with dense PK data and by population PK (PopPK) for all patients. DARO PK from ARASENS were compared with PK data from ARAMIS (NCT02200614; without DOC) to evaluate the impact of DOC on DARO PK. Results: Of 1306 randomized patients, 1305 were included in the full analysis set (DARO, n=651; PBO, n=654). The median treatment duration was longer with DARO vs PBO (41.0 vs 16.7 months) and more DARO-treated patients (45.9% vs 19.1%) were still receiving treatment at primary analysis cutoff (Oct 25, 2021). Almost all patients completed 6 cycles of DOC in both groups (DARO, 87.6%; PBO, 85.5%). The proportion of patients requiring DOC dose modification (interrupted/delayed or reduced) was similar between groups (DARO, 60.0%; PBO, 62.9%). TEAEs led to discontinuation/reduction of DOC in 8.0%/19.9% of DARO patients and 10.3%/19.5% of PBO patients. PopPK analysis indicated that DOC PK in ARASENS was generally consistent with that in the literature. A slight numeric increase in DOC exposure was observed in the DARO + DOC + ADT arm, with 15% higher maximum plasma concentration (geometric mean, 1.93 vs 1.68 µg/mL) and 6% higher area under the concentration-time curve (AUC0-tlast within an 8-hour sampling interval, 2.10 vs 1.99 µg·h/mL) vs PBO + DOC + ADT. This small numeric increase is likely not clinically relevant given the variability in DOC exposure (coefficient of variation, 23%–54%). PK meta-analysis of ARASENS and, which considered patients’ intrinsic characteristics as covariates (eg, age, body weight, region), indicated a 10% lower AUC0-12ss of DARO in patients receiving DOC vs those not receiving DOC, which is not considered clinically relevant. Conclusions: The combination of DARO + DOC + ADT increases overall survival with similar overall incidence of TEAEs and no observed drug-drug interactions between DARO and DOC. DARO can be effectively and safely administered with DOC in patients with mHSPC without clinically relevant changes in PK of DARO or DOC. Clinical trial information: NCT02799602 .

Niraparib (NIRA) with abiraterone acetate and prednisone (AAP) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) and homologous recombination repair (HRR) gene alterations: Second interim analysis (IA2) of MAGNITUDE

170

Background: In the primary analysis of the phase 3 MAGNITUDE study, NIRA/AAP significantly improved outcomes in pts with mCRPC and HRR gene alterations. Here, we report results from IA2 of secondary endpoints in MAGNITUDE. Methods: 423 eligible pts with mCRPC and HRR alterations (HRR+ cohort) were randomized 1:1 to receive NIRA/AAP (n = 212) or placebo (PBO)/AAP (n = 211). At the prespecified IA2, secondary endpoints (time to cytotoxic chemotherapy [TCC], time to symptomatic progression [TSP], overall survival [OS]) were formally assessed and the primary rPFS endpoint was updated in the HRR+ cohort, with sensitivity analysis performed for the subgroup of pts with BRCA alterations. Results: Updated descriptive rPFS results at IA2 (cutoff: June 17, 2022) were consistent with the primary analysis in the HRR+ cohort. In the BRCA subgroup, NIRA/AAP extended median rPFS to 19.5 mos vs 10.9 mos with PBO/AAP. NIRA/AAP led to statistically significant benefit in TSP in the HRR+ cohort with consistent benefit in the BRCA subgroup. Continued consistent improvement of TCC was seen with NIRA/AAP in the HRR+ cohort and in the BRCA subgroup. There was a trend towards improved OS with NIRA/AAP in the BRCA subgroup in the primary stratified analysis and the multivariate analysis (MVA), accounting for imbalances in key baseline characteristics. BRCA pts treated with NIRA/AAP experienced delayed time to worst pain intensity (HR, 0.70; 95% CI, 0.44, 1.12; nominal P = 0.1338) and pain interference (HR, 0.67; 95% CI, 0.40, 1.12; nominal P = 0.1275) compared to PBO/AAP. The safety profile at IA2 was consistent with that of the primary analysis, with no new safety signals observed. Conclusions: With 26.8 months of median follow-up, there was a statistically significant and meaningful clinical benefit in TSP and meaningful clinical benefit in TCC. Additionally, updated rPFS results from MAGNITUDE IA2 were consistent with the primary analysis; OS benefit was not conclusive due to immaturity and will be followed through to final analysis. Taken together, these data continue to support the use of NIRA/AAP in pts with mCRPC and BRCA alterations or select other HRR gene alterations. Clinical trial information: NCT03748641 . [Table: see text]

CYCLONE 3: A phase 3, randomized, double-blind, placebo-controlled study of abemaciclib in combination with abiraterone plus prednisone in men with high-risk, metastatic, hormone-sensitive prostate cancer (mHSPC)

TPS289

Background: Landmark trials have established a survival benefit for novel hormonal agents (NHA) added to androgen deprivation therapy (ADT) for mHSPC. Yet, there is a significant medical need to expand therapeutic options, especially for pts with high-risk mHSPC who experience poorer outcomes. Abemaciclib is an oral selective inhibitor of cyclin-dependent kinase 4 and 6 (CDK4 & 6) dosed on a continuous schedule, approved for the treatment of node-positive high-risk early-stage and advanced or metastatic HR+, HER2- breast cancer. Analogous to the estrogen receptor signaling pathway in breast cancer, there is evidence that the androgen receptor axis activates CDK4 & 6 to sustain prostate cancer cell proliferation, and upregulation of cyclin D1 is a potential mechanism of resistance to NHA therapy. In preclinical models, abemaciclib induces cell cycle arrest and inhibition of prostate tumor growth. Methods: CYCLONE 3 (NCT05288166) is a global, randomized, double-blind, placebo-controlled study evaluating the addition of abemaciclib to abiraterone+prednisone (AP) in pts with high-risk mHSPC. Approximately 900 pts with high-risk mHSPC defined by ≥4 bone metastasis and/or visceral disease will be randomised in a 1:1 ratio to the AP + abemaciclib or AP + placebo arm. Up to 3 months of ADT prior to randomization is permitted; prior D for mHSPC will be excluded per planned protocol amendment. Pts who have not undergone orchiectomy will continue ADT. Stratification factors are de novo mHSPC and visceral metastases. Primary endpoint is investigator-assessed radiographic progression-free survival (rPFS). Key secondary endpoints include rPFS assessed by blinded independent central review, castration-resistant prostate cancer-free survival, overall survival, time to pain progression, safety and pharmacokinetics. Enrollment is open at approximately 270 sites across 25 countries. Clinical trial information: NCT05288166 .

Efficacy of subsequent treatments in patients who progressed to mCRPC following treatment with apalutamide for nonmetastatic castration-resistant prostate cancer (nmCRPC): A post-hoc analysis of the SPARTAN phase III trial

157

Background: Apalutamide (Apa) delays the onset of metastases and extends survival in nmCRPC. However, the benefit of subsequent therapy for metastatic castration resistant prostate cancer (mCRPC) following progression on Apa remains inadequately explored. Methods: A post-hoc analysis of SPARTAN, a randomized phase III (NCT01946204), double-blind, placebo-controlled trial with Apa for the treatment of men with nmCRPC was undertaken in order to assess the impact of post-protocol treatment. Patients included in this analysis were SPARTAN patients who developed mCRPC while on Apa and received a first subsequent therapy for mCRPC (the “Next Cohort”). The index date of the analysis was the initiation of first subsequent treatment for mCRPC. The baseline characteristics of the Next Cohort (reported from the time of initial randomization because updated characteristics at the index date could not be derived) were compared to those of the ITT Apa arm in SPARTAN. Subsequent overall survival (sOS) and subsequent progression-free survival per physician assessment (sPFS) were calculated from the index date using Kaplan-Meier method. Results: At study completion, 237 patients remained on Apa without progression, while 311 were included in the Next Cohort. Of these, 241 (77.5%) received abiraterone acetate plus prednisone (AAP) provided by the sponsor as an option as first subsequent treatment, 29 (9.3%) received docetaxel; 20 (6.4%) enzalutamide and 21 other treatments (6.8%). Compared to the ITT Apa arm in SPARTAN, a higher proportion of the Next Cohort had PSA doubling time ≤6 months (79.1% vs 71.5%) and a PSA value above median at baseline, and experienced poorer PSA response (51% PSA90 overall response rate vs 62%) whilst on apalutamide treatment. The median sPFS and sOS were 6.8 months (95% confidence interval, CI, 5.8-7.9) and 20.0 months (95% CI, 17.0-22.6), respectively. Choice of subsequent next treatment did not appear to have an impact on sPFS and sOS. Conclusions: Limitations of this analysis include its retrospective nature and the lack of randomization to first line mCRPC therapy and related potential confounding, and the inclusion of patients who had progressed at SPARTAN study completion with associated poorer prognosis. Nevertheless, the analysis suggests comparable efficacy of selected first line mCRPC therapies, following progression on Apa for nmCRPC. Clinical trial information: NCT01946204 . [Table: see text]

Association of prostate-specific antigen (PSA) response and overall survival (OS) in patients with metastatic hormone-sensitive prostate cancer (mHSPC) from the phase 3 ARASENS trial

5078

Background: Reductions in PSA level have been associated with improved OS in patients (pts) with mHSPC. In ARASENS (NCT02799602), darolutamide (DARO) + androgen-deprivation therapy (ADT) in combination with docetaxel significantly reduced the risk of death by 32.5% (hazard ratio [HR] 0.675; 95% confidence interval [CI] 0.568–0.801; P< 0.0001) vs ADT + docetaxel in pts with mHSPC. We report the association between PSA response and OS from ARASENS. Methods: Pts with mHSPC were randomized 1:1 to DARO 600 mg twice daily or matching PBO + ADT and docetaxel. Serum PSA was measured at screening and every 12 weeks. Exploratory analyses included time to PSA progression (≥25% increase from PSA nadir [lowest or at study entry] and PSA increase ≥2 ng/mL ≥12 weeks from nadir [both confirmed by a second value ≥3 weeks later]) and undetectable PSA (< 0.2 ng/mL for 2 samples ≥3 weeks apart) at 24, 36, and 52 weeks and any time during treatment. Comparisons between treatment groups were performed using the Cochran-Mantel Haenszel test stratified by randomization stratification factors (metastatic spread according to TNM classification and alkaline phosphatase levels at study entry). Post hoc landmark analyses evaluated the association between undetectable PSA at weeks 24 and 36 and OS for the overall population. Results: Of 1306 randomized pts, 1305 were included in the full analysis set (DARO 651; PBO 654), both with ADT and docetaxel. Median (range) PSA levels at study entry were 30.3 (0.0–9219.0) and 24.2 (0.0–11,947.0) ng/mL, respectively. DARO significantly prolonged time to PSA progression (HR 0.255; 95% CI 0.208–0.313; P< 0.0001). Undetectable PSA was achieved in more pts receiving DARO (48.7%) vs PBO (23.9%) at 24 weeks, and the rate continued to increase at 36 and 52 weeks in the DARO group to 57.1% and 60.2%, respectively, vs minimal change in the PBO group (25.1% and 26.1%). Undetectable PSA levels at any time were achieved in 67.3% in the DARO group and 28.6% in the PBO group. A treatment difference in undetectable PSA based on non-overlapping 95% CIs was observed at all time points. For the overall population, OS was improved for pts who achieved undetectable PSA levels vs those who did not at 24 weeks (HR 0.398; 95% CI 0.321–0.493) and 36 weeks (HR 0.351; 95% CI 0.284–0.434). Additional baseline and safety data by PSA level will be reported. Conclusions: The combination of DARO + ADT and docetaxel significantly prolonged the time to PSA progression and more pts receiving DARO vs PBO achieved undetectable PSA levels, reflecting strong PSA response over time. In pts with mHSPC, achievement of undetectable PSA at 24 and 36 weeks was associated with improved OS, with risk of death reduced by 60% and 65%, respectively, vs those who did not achieve undetectable PSA at 24 and 36 weeks. Clinical trial information: NCT02799602.

Health-related quality of life (HRQoL) and pain in the MAGNITUDE study of niraparib (NIRA) with abiraterone acetate and prednisone (AAP) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) and homologous recombination repair (HRR) gene alterations

5060

Background: Results from the international, randomized, double-blind, phase 3 MAGNITUDE study demonstrated that NIRA + AAP improved radiographic progression-free survival, time to cytotoxic chemotherapy, and time to symptomatic progression, with manageable toxicity in pts with mCRPC and HRR alterations (9-gene panel). Here, we report HRQoL and pain in MAGNITUDE. Methods: Eligible pts with mCRPC and HRR alterations were randomized 1:1 to NIRA + AAP or placebo (PBO) + AAP orally daily in 28-day cycles. Pts had ECOG status ≤1 and a Brief Pain Inventory–Short Form (BPI-SF) worst pain score ≤3 in prescreening. HRQoL assessments on day 1 of specified cycles included Functional Assessment of Cancer Therapy–Prostate (FACT-P) and BPI-SF. Changes from baseline were compared between treatment arms using repeated measures analysis. Proportional hazards regression models were used to compare time to deterioration (TTD) in worst pain intensity between arms. Results: Compliance for FACT-P and BPI-SF was > 80%. Most pts maintained low pain levels over time. Repeated measures analyses showed no clinically meaningful differences in pain over time or between arms. Median TTD in pain intensity was not reached in either arm. At the 25th percentile, there was a trend toward longer TTD in pain intensity with NIRA + AAP vs PBO + AAP (11.1 vs 10.1 mo; HR, 0.87; 95% CI, 0.61-1.24). HRQoL was maintained with NIRA + AAP, with no clinically meaningful differences in FACT-P total score over time or between arms. There was a trend toward greater worsening in early cycles on FACT-P physical wellbeing with NIRA + AAP vs PBO + AAP, driven by events within the known safety profile of NIRA + AAP (worsening of side effect bother, lack of energy, and nausea); however, overall, most pts reported minimal side effect burden (Table). Conclusions: In MAGNITUDE, most pts maintained low pain levels and positive HRQoL over time, with no clinically meaningful differences between treatment arms, further supporting the use of NIRA + AAP in pts with mCRPC and HRR alterations. Side effect burden was perceived as low in both arms. Although more pts on NIRA+AAP reported worsening side effects, the symptoms were generally perceived as mild. Clinical trial information: NCT03748641. [Table: see text]

Patient (pt) population and radiation therapy (RT) type in the long-term phase 3 double-blind, placebo (PBO)-controlled ATLAS study of apalutamide (APA) added to androgen deprivation therapy (ADT) in high-risk localized or locally advanced prostate cancer (HRLPC)

5084

Background: Current management of HRLPC includes long-term ADT with primary RT. Despite definitive primary treatment, these pts have a high risk of metastasis and death. The phase 3 ATLAS study (NCT02531516) is investigating whether treatment intensification with the addition of APA to neoadjuvant and adjuvant treatment with gonadotropin-releasing hormone agonist (GnRHa) and external beam radiation therapy (EBRT) will improve metastasis-free survival (MFS) in high-risk pts. Here we describe (1) the distribution of baseline characteristics in this high-risk pt population and (2) the application of different RT regimens reflecting recent international guidelines and clinical practice changes for pts with HRLPC. Methods: Eligible HRLPC pts (Gleason score [GS] ≥ 8 or 7 and prostate-specific antigen [PSA] ≥ 20 ng/mL and stage ≥ cT2c), with ECOG PS 0/1 and Charlson Comorbidity Index (CCI) ≤ 3 are stratified by GS, pelvic nodal status, use of brachytherapy boost, and region; pts are randomized 1:1 to APA or PBO plus GnRHa for 30 (28-d) treatment cycles. Study treatment is applied neoadjuvant/concurrent to RT with APA 240 mg/d vs bicalutamide 50 mg/d for 4 cycles; another 26 cycles are completed adjuvantly after RT with APA 240 mg/d vs PBO. Primary end point is MFS (time from randomization to first distant metastasis on CT/MRI/bone scan by independent central review blinded to treatment or death from any cause). Imaging is conducted at baseline and q6m from biochemical failure until MFS. The protocol has been amended to include PET imaging (PSMA, fluciclovine, or choline). Results: Pts (N = 1503) were randomized at 266 sites in 24 countries in North America, Latin America, Europe, and Asia. The study is fully enrolled, but ongoing. Baseline characteristics for the total population: median age, 67 yrs; ECOG PS 0/1; 89%/11%; tumor classification at study entry: high-risk, 66%/very high–risk, 34%; median PSA, 6.3 ng/mL; cT2, 44%/cT3, 50%; cN1, 13%. In 90% of ATLAS pts, RT used was standard EBRT to prostate/pelvis over 6-8 weeks (cumulative 78-81 Gy); in 10%, recent hypofractionation schedules (per CHHiP or NRG/RTOG 0415) were applied (20x3 Gy/d or 28x2.5 Gy/d). 5.6% of pts had EBRT combined with brachytherapy (per ASCENDE-RT). Conclusions: Baseline characteristics of the ATLAS study population are reflective of pts with high- and very high–risk features and pelvic nodal involvement undergoing primary RT in clinical practice. The RT schedules applied reflect recent evidence and guideline changes for the use of hypofractionation in this pt population. ATLAS is an example of how RT can be included in phase 3 trials of HRLPC, in combination with next-generation androgen receptor inhibitors (eg, APA). Clinical trial information: NCT02531516.

Gene-by-gene analysis in the MAGNITUDE study of niraparib (NIRA) with abiraterone acetate and prednisone (AAP) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) and homologous recombination repair (HRR) gene alterations

5020

Background: NIRA + AAP significantly improved outcomes in pts with mCRPC and HRR gene alterations in the Phase 3 MAGNTUDE study. There is a paucity of data supporting use of PARP inhibitors in pts with HRR gene alterations other than BRCA1/2. We report on the efficacy of NIRA + AAP in pts with mCRPC and a qualifying single gene HRR alteration other than BRCA1/2. Methods: A pre-specified analysis was undertaken of the primary endpoint (radiographic progression-free survival [rPFS] by BICR), secondary endpoints (time to cytotoxic chemotherapy [TCC], time to symptomatic progression [TSP], overall survival [OS]), as well as time to PSA progression (TPSA) and overall response rate (ORR) across 186 pts (91 randomized to NIRA + AAP, 95 to PBO + AAP) with an alteration in the ATM, BRIP1, CDK12, CHEK2, FANCA, HDAC2, or PALB2 gene (excluding cooccurring alterations) . This analysis of individual alterations was not powered for formal statistical inference. Given the rarity of some alterations, groups based on functional similarity are also presented. Results: (Table). Pts with PALB2 or CHEK2 alterations had consistent improvement across all endpoints. In pts with ATM alterations benefit was observed in TCC, TSP, TPSA and ORR. There was benefit only in TPSA and ORR for pts with CDK12 alterations. When combined into functional groups, pts with an alteration in the HRR-Fanconi pathway ( BRIP1, FANCA, and PALB2) as well as pts with a HRR associated alteration ( CHEK2 or HDAC2) showed improvement in all endpoints. Conclusions: These data support the overall conclusions of the MAGNITUDE primary analysis and support benefit of NIRA + AAP in pts with HRR mutations beyond BRCA1/2. Clinical trial information: NCT03748641. [Table: see text]

Assessing intermediate clinical endpoints (ICE) as potential surrogates for overall survival (OS) in men with metastatic hormone-sensitive prostate cancer (mHSPC)

5006

Background: We hypothesized that radiographic progression free survival (rPFS) and clinical PFS (cPFS) are valid surrogates for OS in men with mHSPC and could potentially be used to expedite phase 3 clinical trials. This hypothesis was investigated by the STOPCAP M1 Collaboration. Methods: We obtained individual patient data (IPD) from 13/26 eligible randomized trials comparing treatment regimens (androgen deprivation therapy (ADT) or ADT + docetaxel in the control or research arms) in mHSPC. We evaluated the surrogacy of rPFS and cPFS as potential ICEs. rPFS was defined as time from randomization to radiographic progression (defined per protocol) or death from any cause whichever occurred first; cPFS was defined as time from randomization to date of radiographic progression, symptoms, initiation of new treatment, or death, whichever occurred first. OS was defined as time from randomization to death from any cause, if patients had not died they were censored at the date of last follow-up. We implemented a two-stage meta-analytic validation model where conditions of trial level and patient level surrogacy had to be met. We computed the surrogate threshold effect (STE), which is the minimum ICE treatment effect necessary to estimate a non-zero effect on OS. Results: IPD from 8592 patients randomized from 1994-2012 from 13 trials were pooled for a stratified analysis. There were 5377 deaths, of which 3971 (74%) were due to prostate cancer. The median follow-up for surviving patients was 75.6 months. In addition, there were 6227 rPFS and 6314 cPFS events. The median OS, rPFS and cPFS were 49.4, 26.8 and 25.2 months, respectively. The STE was 0.82 for rPFS and 0.84 for cPFS. Conclusions: Both rPFS and cPFS appear to be valid surrogate endpoints for OS. A surrogate threshold effect of 0.82 or higher makes it viable for either rPFS or cPFS to be used as the primary endpoint as a surrogate for OS in phase 3 mHSPC trials and would expedite trial conduct. Validation of these ICEs in trials with drugs having other mechanisms of action is planned. Clinical trial information: Several. [Table: see text]

CYCLONE 2: A phase 2/3, randomized, placebo-controlled study of abiraterone acetate plus prednisone with or without abemaciclib in patients with metastatic castration-resistant prostate cancer

TPS198

Background: Despite recent advances, nearly all patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) experience disease progression and cancer-specific mortality. Persistent or reactivated androgen receptor (AR) signaling and/or activation of pathways in cross-talk with AR signaling are key drivers of mCRPC progression. Evidence suggests that AR signaling promotes translation of D-type cyclins resulting in cyclin-dependent kinase 4 and 6 (CDK4&6) activation and cell cycle progression. Abemaciclib is an oral selective inhibitor of CDK4&6 dosed on a continuous schedule, that is FDA-approved in combination with endocrine therapy or as monotherapy to treat HR+, HER2- metastatic breast cancer pts. Preclinical studies with prostate cancer cell lines and xenograft models showed that abemaciclib induces cell cycle arrest and tumor growth inhibition. The hypothesis is that addition of abemaciclib to AR targeted therapy may be an effective treatment for mCRPC pts. Methods: CYCLONE 2 (NCT03706365) is a phase 2/3, randomized, double-blind, multicenter, placebo-controlled study to assess the safety and efficacy of abemaciclib in combination with abiraterone acetate plus prednisone (AA+P) in pts with mCRPC. CYCLONE 2 is an adaptive study which is designed in three parts. Part 1 is a 30-patient safety lead-in to determine the recommended phase 2 dose (RP2D; 150 mg or 200 mg, twice daily) of abemaciclib in combination with AA (1000 mg, once daily) + P (5 mg, twice daily). In part 2, 150 pts are randomized 1:1 to AA+P with abemaciclib at the RP2D or placebo. The study expands to enroll an additional 170 pts in Part 3 if prespecified expansion criteria are met at a planned adaptive interim analysis performed by an independent data monitoring committee (IDMC). Pts with mCRPC evidenced by radiographic and/or PSA progression during continuous ADT are eligible. Prior docetaxel for mHSPC is permitted. Systemic anti-cancer therapy for mCRPC and prior novel hormonal agents are exclusionary. The primary objective is radiographic progression free survival (rPFS; per RECIST1.1 for soft tissue and PCWG3 for bone). Secondary objectives include safety, objective response rate, duration of response, time to symptomatic and PSA progression, overall survival, and pharmacokinetics. Status: Enrollment in Part 1 & 2 is completed. Based on the recommendation from the IDMC, Part 3 was opened in June 2021 and enrolls pts from about 112 sites across 12 countries. Clinical trial information: NCT03706365.

Phase 3 MAGNITUDE study: First results of niraparib (NIRA) with abiraterone acetate and prednisone (AAP) as first-line therapy in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) with and without homologous recombination repair (HRR) gene alterations

12

Background: Approximately 20% of mCRPC has alterations in genes associated with HRR and is responsive to PARP inhibitors (PARPi) such as NIRA. Combined PARPi with androgen receptor pathway targeting may also benefit unselected mCRPC. MAGNITUDE assessed whether adding NIRA to AAP improves outcomes in pts with mCRPC with or without alterations in HRR associated genes. Methods: MAGNITUDE (NCT03748641) is a randomized, double-blind phase 3 study. In eligible mCRPC pts, ≤4 mos of prior AAP for mCRPC was allowed. Pts with (HRR biomarker [BM]+; ATM, BRCA1, BRCA2, BRIP1, CDK12, CHEK2, FANCA, HDAC2, PALB2) and without specified gene alterations (HRR BM-) were randomized 1:1 to receive NIRA 200 mg once daily + AAP or placebo (PBO) + AAP. Primary endpoint was radiographic progression-free survival (rPFS) assessed by blinded independent central review (BICR) in the BRCA1/2 group followed by all HRR BM+ pts. Secondary endpoints were time to initiation of cytotoxic chemotherapy (TTCC), time to symptomatic progression (TTSP) and overall survival (OS). Other endpoints included time to PSA progression (TTPP) and objective response rate (ORR). Results: 423 HRR BM+ pts were randomized to NIRA + AAP (n = 212) or PBO + AAP (n = 211). Median age was 69, 23% had prior AAP, 21% had visceral metastases, and 53% had BRCA1/2 mutations. Median follow-up was 18.6 mos. NIRA + AAP significantly improved rPFS by BICR in the BRCA1/2 subgroup and in all HRR BM+ pts, reducing the risk of progression or death by 47% (16.6 vs 10.9 mo) and 27% (16.5 vs 13.7 mo) respectively (Table), vs PBO + AAP. Investigator assessed rPFS was consistent with BICR. NIRA + AAP delayed TTCC, TTSP, and TTPP and improved ORR in HRR BM+ pts (Table). First interim analysis of OS is immature. The preplanned futility analysis in 233 HRR BM- pts showed no benefit of adding NIRA to AAP in the prespecified composite endpoint (first of PSA progression or rPFS; HR, 1.09; 95% CI, 0.75-1.57). No new safety signals were seen. In HRR BM+ pts, 67% and 46.4% had grade 3/4 AEs and 9% and 3.8% discontinued treatment in the NIRA + AAP and PBO + AAP arms, respectively. There were no clinically significant differences in overall quality of life (FACT-P). Conclusions: NIRA + AAP improves rPFS and other clinically relevant outcomes in pts with mCRPC and alterations in HRR associated genes. There was no evidence of benefit with the addition of NIRA to AAP in HRR BM- pts with mCRPC. Clinical trial information: NCT03748641. [Table: see text]

Overall survival with darolutamide versus placebo in combination with androgen-deprivation therapy and docetaxel for metastatic hormone-sensitive prostate cancer in the phase 3 ARASENS trial

13

Background: Darolutamide (DARO) is a structurally distinct and highly potent androgen receptor inhibitor that demonstrated improved overall survival (OS) and metastasis-free survival vs placebo (PBO) and a low incidence of treatment-emergent adverse events (TEAEs) in patients (pts) with nonmetastatic castration-resistant prostate cancer (CRPC). We investigated whether DARO in combination with standard androgen-deprivation therapy (ADT) + docetaxel would increase OS in pts with metastatic hormone-sensitive prostate cancer (mHSPC) in the ARASENS study (NCT02799602). Methods: This international, double-blind, phase 3 study enrolled pts with mHSPC and ECOG PS 0/1 who were randomized 1:1 to DARO 600 mg twice daily or matching PBO in addition to ADT + docetaxel. Randomization was stratified by extent of disease according to TNM (M1a vs M1b vs M1c) and alkaline phosphatase levels ( < vs ≥ upper limit of normal). The primary endpoint was OS. Secondary efficacy endpoints included time to CRPC, time to pain progression, time to first symptomatic skeletal event (SSE), and time to initiation of subsequent systemic antineoplastic therapies. Safety was also assessed. Results: From Nov 2016 to June 2018, 1306 pts were randomized, 651 to DARO and 655 to PBO, in combination with ADT + docetaxel. Median age was 67 y in both arms. At the primary data cutoff (Oct 25, 2021), DARO significantly decreased the risk of death by 32.5% vs PBO (HR 0.675, 95% CI 0.568–0.801; P < 0.0001). The significant improvement in OS was observed even though substantially more pts received subsequent life-prolonging systemic antineoplastic therapy in the PBO arm (75.6%) vs the DARO arm (56.8%). The significant OS benefit was consistent across prespecified subgroups. In addition, DARO significantly delayed time to CRPC versus PBO (HR 0.357, 95% CI 0.302–0.421; P < 0.0001). Time to pain progression was also significantly longer with DARO vs PBO (HR, 0.792, 95% CI 0.660–0.950; P= 0.0058), as were time to first SSE and time to initiation of subsequent systemic antineoplastic therapy. TEAEs were similar between treatment arms, and the incidences of the most common TEAEs (≥10%) were highest during the overlapping docetaxel treatment period for both arms, with grade 3/4 TEAEs of 66.1% for DARO and 63.5%for PBO, mainly due to neutropenia (33.7% vs 34.2%, respectively). TEAEs led to treatment discontinuation in 13.5% of pts in the DARO arm and 10.6% of pts in the PBO arm. Conclusions: In pts with mHSPC, early treatment combining DARO with ADT + docetaxel significantly increased OS and improved key secondary endpoints vs ADT + docetaxel alone. The incidence of TEAEs was similar in the two treatment arms. Clinical trial information: NCT02799602.

Efficacy and safety outcomes of darolutamide in patients with nonmetastatic castration-resistant prostate cancer with comorbidities and concomitant medications from ARAMIS

256

Background: Patients (pts) with nonmetastatic castration-resistant prostate cancer (nmCRPC) are primarily older, have comorbidities, and take concomitant medications. Darolutamide (DARO), a structurally distinct and highly potent androgen receptor inhibitor, significantly reduced the risk of metastasis by ̃2 years and the risk of death by 31% versus placebo (PBO) and demonstrated favorable safety and tolerability in the phase 3 ARAMIS trial. DARO also has low potential for drug−drug interactions. This post hoc analysis of ARAMIS evaluated overall survival (OS) and safety in pts with ongoing comorbidities and concomitant medications. Methods: Pts with nmCRPC were randomized 2:1 to DARO (n=955) or PBO (n=554) while continuing androgen-deprivation therapy. At the final data cutoff (Nov 15, 2019), OS and adverse events (AEs) were evaluated in pts with a median of ≤ and >6 comorbidities or ≤ and >10 concomitant medications in the double-blind period. HRs (95% CIs) were determined from univariate analysis using Cox regression. Results: The majority of pts had ≥6 comorbidities (53%; 795/1509) or received ≥10 concomitant medications (54%; 813/1509). For pts with ≤6 and >6 comorbidities, DARO prolonged OS vs PBO (HR 0.65 and 0.73, respectively). OS benefit of DARO vs PBO was consistent for pts with metabolic, cardiovascular (CV), and other comorbid disorders (HR range: 0.39–0.88). For pts receiving ≤10 and >10 concomitant medications, OS was prolonged with DARO vs PBO (HR 0.76 and 0.66, respectively). Subgroups of pts receiving concomitant medications for gastrointestinal/metabolic disorders, CV disease, urologic disorders, and pain/inflammation achieved similar OS benefit with DARO vs PBO (HR range: 0.45–0.80). Incidence of AEs and AEs leading to treatment discontinuation with DARO was comparable to PBO across subgroups by number of comorbidities and concomitant medications (Table). Conclusions: The OS benefit and safety of DARO remained consistent with that observed in the overall ARAMIS population, even in patients with a high number of comorbidities or concomitant medications. Clinical trial information: NCT02200614. [Table: see text]

Association between patient-reported outcomes (PROs) and changes in prostate-specific antigen (PSA) in patients (pts) with advanced prostate cancer treated with apalutamide (APA) in the SPARTAN and TITAN studies

73

Background: In phase 3 placebo (PBO)-controlled studies, addition of APA to androgen deprivation therapy (ADT) improved overall survival, resulted in rapid and deep PSA declines, and reduced risk of disease progression while preserving health-related quality of life (HRQoL) in nonmetastatic castration-resistant prostate cancer (nmCRPC; SPARTAN) and metastatic castration-sensitive prostate cancer (mCSPC; TITAN). This post hoc analysis evaluated the association of a deep PSA decline with PROs in these studies. Methods: Pts on ADT were randomized to APA (240 mg QD) or PBO: SPARTAN 2:1 (N = 1,207; APA n = 806), TITAN 1:1 (N = 1,052; APA n = 525). Each cycle was 28 d. PROs were assessed using Functional Assessment of Cancer Therapy-Prostate (FACT-P), Brief Pain Inventory-Short Form (BPI-SF; TITAN only), and Brief Fatigue Inventory (BFI; TITAN only) at baseline, specific cycles during study treatment, and post progression up to 1 yr. A landmark analysis at Month 3 evaluated association between deep PSA decline (≤ 0.2 ng/mL) and time to subsequent deterioration in PROs (defined as decrease ≥ 10 points FACT-P total, ≥ 3 points Physical Wellbeing, ≥ 30% baseline for BPI-SF worst pain, or ≥ 2 points for BFI worst fatigue). At time of the landmark analysis, only pts continuing treatment were included; all deep PSA responses after, and all PRO deterioration events before, were ignored. Time-to-event end points were analyzed by Kaplan-Meier method and Cox proportional hazards model. Results: Median treatment durations were 32.9 mo (SPARTAN) and 39.3 mo (TITAN). Per assessment, > 90% (SPARTAN, cycles 1-81) and > 50% (TITAN, cycles 1-33) of eligible pts completed FACT-P; BPI-SF and BFI, both > 62% (TITAN, cycles 1-33). Pts in either study who achieved PSA ≤ 0.2 ng/mL at Month 3 had a lower risk of deterioration in FACT-P total or Physical Wellbeing (Table). Pts in TITAN with PSA ≤ 0.2 ng/mL at Month 3 had a lower risk of BPI-SF worst pain intensity or BFI worst fatigue intensity progression (Table). Conclusions: Deep and rapid PSA responses with APA were associated with prolonged time to deterioration in HRQoL, FACT-P Physical Wellbeing, BPI-SF worst pain intensity, and BFI worst fatigue intensity in pts with advanced PC. Clinical trial information: NCT02489318 (TITAN); NCT01946204 (SPARTAN). [Table: see text]

Darolutamide (DARO) tolerability from extended follow up and treatment response in the phase 3 ARAMIS trial

5079

Background: Patients (pts) with nonmetastatic castration-resistant prostate cancer (nmCRPC) need therapy that prolongs survival with little added toxicity, thus preserving quality of life. The second-generation androgen receptor inhibitors (ARIs) including DARO, apalutamide, and enzalutamide offer durable survival in nmCRPC but differences exist in AE profiles (eg, fatigue, falls, fractures, rash, mental impairment, and hypertension) that can limit daily activities. These AEs may require dose modifications and limit pts’ willingness to continue treatment, with an adverse impact on efficacy. DARO is a structurally distinct ARI that significantly extended metastasis-free survival and overall survival (OS) vs placebo (PBO) in ARAMIS (NCT02200614), with minimal AE risk. We report tolerability from extended follow-up and treatment response analyses from ARAMIS. Methods: Pts with nmCRPC (N=1509) were randomized 2:1 to DARO or PBO with androgen deprivation therapy. The ARAMIS trial was unblinded at the primary analysis, after which all pts could receive open-label (OL) DARO. Tolerability was assessed every 16 weeks. Pharmacodynamic modeling investigated the association between treatment response (maximum prostate-specific antigen [PSA] decline from baseline) and OS at 2 years using a Cox proportional hazards model. Results: As shown in the table, DARO remained well tolerated over the double-blind (DB) and OL periods: 98.8% of pts on DARO received the full planned dose and almost all pts with dose modifications were able to resume and re-establish the planned dose (DARO 89.6% vs PBO 89.7%). Discontinuation of DARO due to AEs increased slightly from the DB period (9.0%) to the DB+OL period (10.5%). Pharmacodynamic modeling showed that longer OS was positively associated with maximum PSA decline in DARO-treated pts. Conclusions: DARO remained well tolerated with extended treatment at the recommended dose of 600 mg twice daily. Almost all pts with nmCRPC were able to receive the full planned dose, increasing the likelihood of clinical benefit from effective disease control (PSA decline) and prolonged survival. Tolerability of different ARIs in the real world should be assessed. Clinical trial information: NCT02200614. [Table: see text]

CYCLONE 1: A phase 2 study of abemaciclib in patients with metastatic castration-resistant prostate cancer (mCRPC) previously treated with a novel hormonal agent and taxane-based chemotherapy

TPS5086

Background: In cancer cells, the cyclin-dependent kinases 4 and 6 (CDK4 & 6)/retinoblastoma protein (Rb) pathway is commonly altered, resulting in uncontrolled cell cycle entry and proliferation. CDK4 & 6 inhibitors represent a major advance in the management of hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced or metastatic breast cancer (ABC or MBC, respectively). Abemaciclib is an oral selective inhibitor of CDK4 & 6 administered on a continuous dosing schedule, approved in combination with endocrine therapy for HR+, HER2- ABC or MBC. In addition, abemaciclib is also approved by the FDA as monotherapy for HR+, HER2- ABC or MBC following endocrine therapy and prior chemotherapy in the metastatic setting. Similar to the estrogen receptor signaling pathway in breast cancer cells, there is evidence that the androgen receptor axis activates CDK4 & 6 to sustain prostate cancer cell proliferation and survival. Preclinical studies in prostate cancer cell lines and xenograft models showed that abemaciclib exhibits single agent activity by inducing cell cycle arrest and tumor growth inhibition. Clinical activity of abemaciclib in combination with abiraterone and prednisone is investigated in a randomized phase 2 study in the first-line mCRPC setting (CYCLONE 2, NCT03706365). Despite recent advances, management of heavily pretreated mCRPC remains a major clinical challenge. Herein, we hypothesize that mCRPC patients whose disease progressed after novel hormonal agents (NHA) and taxane therapies may derive therapeutic benefit from single agent abemaciclib. Methods: CYCLONE 1 is a phase 2, single-arm, multicenter study to assess the safety and efficacy of abemaciclib monotherapy in 40 patients with mCRPC progressing after ≥1 NHA and 2 taxane regimens. Patients will be enrolled at time of prostate specific antigen (PSA) or radiographic progression per PCWG3 criteria and have at least 1 measurable lesion per RECIST 1.1. Metastatic tumor tissue (fresh biopsy or archival material <12 weeks) is required at baseline for biomarker analysis. Patients will receive abemaciclib 200 mg twice daily until unacceptable adverse events or disease progression. The primary objective is investigator-assessed objective response rate (ORR). Key secondary objectives include safety, radiographic progression-free survival, overall survival, PSA response rate, time to PSA progression, time to symptomatic progression, Ki-67 expression, patient-reported outcomes, and pharmacokinetics. Assuming an ORR of 15%, the study has over 73% power to observe a response rate of at least 12.5%. Accrual began in January 2021. Clinical trial information: NCT04408924.

Molecular determinants associated with long-term response to apalutamide (APA) in nonmetastatic castration-resistant prostate cancer (nmCRPC)

8

Background: SPARTAN, a phase 3 placebo (PBO)-controlled study in patients (pts) with nmCRPC, showed that APA plus androgen deprivation therapy (ADT) significantly improves metastasis-free survival compared with PBO + ADT. This exploratory analysis investigated potential biological signatures of pts with long-term responses to APA and PBO. Methods: The biomarker cohort of SPARTAN was characterized as long-term responders (LTR) or early progressors (EP) based on time to metastasis, and separated into quartiles for APA and PBO groups. Pts progressing in the first quartile (APA, 21; PBO, 17), with shortest time to metastatic event, were classified as EP, those progressing in the last quartile (APA, 39; PBO, 20) as LTR. Gene expression profiles were generated from 233 archival primary prostate tumors. Predefined gene signatures indicative of cancer biology were compared between LTR and EP groups within the APA and PBO arms using 2 sample t tests. Signatures associated with LTR and EP were identified using p values of less than 0.05. Results: Median time to metastatic progression was 40.5 months in APA pts and 22 months in PBO pts in the LTR group and 7.3 and 3.6 months in APA and PBO pts, respectively, in the EP group. Signatures categorized into 3 general mechanistic classes (immune regulation, proliferation, and hormone dependence) associated with LTR on APA included increased T cell activity reflected by T cell activation ( p = 0.0045), stimulation ( p = 0.0642), cytokine response ( p = 0.0489), and interferon production (gamma response p = 0.0227 ), and decreased T cell exclusion ( p = 0.0652), low proliferative capacity ( p = 0.0435), and increased hormonal dependence ( p = 0.0485). High risk (DECIPHER p = 0.0406, metastatic potential p = 0.0077), hormone nonresponsive (basal p = 0.0115; androgen receptor activity-low, p = 0.0437), and neuroendocrine-like tumors ( p = 0.0125) were associated with early progression on treatment with PBO. Conclusions: Although the data require confirmation in larger studies, these molecular determinants may have utility in selecting pts with nmCRPC who may derive the most benefit from APA and other androgen signaling inhibitors. Clinical trial information: NCT01946204.

Safety of darolutamide (DARO) for nonmetastatic castration-resistant prostate cancer (nmCRPC) from extended follow-up in the phase III ARAMIS trial

239

Background: DARO is a structurally distinct androgen receptor inhibitor (ARI) approved for treating nmCRPC. In ARAMIS, DARO significantly reduced the risk of death by 31% (HR = 0.69; 95% CI: 0.53-0.88; p = 0.003) and prolonged median metastasis-free survival vs placebo (PBO; 40.4 months vs 18.4 months; HR = 0.41; 95% CI: 0.34-0.50; p < 0.001). Adverse events (AEs) of interest commonly associated with ARI therapy, such as fatigue, falls, fractures, rash, mental impairment, and hypertension, as well as interactions between ARIs and concomitantly administered drugs, can impact patient daily life. In the final analysis of the double-blind (DB) period of the ARAMIS trial, DARO had a favorable safety profile, showing ≤2% difference vs PBO for most AEs of interest. Fatigue was the only AE with > 10% incidence with DARO. The incidence of permanent discontinuation due to AEs was also similar between DARO and PBO (8.9% vs 8.7%). Here we present safety data for prolonged treatment with DARO from the final analysis of the DB + open-label (OL) period of ARAMIS. Methods: Patients (pts) with nmCRPC (N = 1509) were randomized 2:1 to DARO or matched PBO while continuing androgen deprivation therapy. The data cut-off for the primary analysis of the DB period was September 3, 2018. Study unblinding occurred on November 30, 2018, after which pts in the DARO arm still receiving study treatment continued with OL DARO. The data cut-off for final analysis of the DB+OL period was November 15, 2019. Results: At the final analysis, the median treatment duration for pts randomized to DARO was 18.5 months for the DB period and 25.8 months for the DB+OL period. At the final cut-off date, 48.8% of patients in the DARO DB+OL group were still receiving DARO treatment. The increase in the incidence of any-grade AEs (85.7% vs 89.8%) and serious AEs (26.1% vs 32.1%) between the DB and DB+OL period was small. Between the DB and DB+OL periods, only minor numerical changes for ARI-associated AEs were observed. When the incidences were corrected for exposure, there were minimal differences between the DB and DB+OL period, e.g., the fracture rate was 3.4 vs 4.0 per 100 patient-years for the DB vs DB+OL periods, respectively. Fatigue was the only ARI-associated AE of interest that exhibited > 10% incidence in the DARO arm during the DB+OL period. The incidence of permanent discontinuation of DARO due to AEs increased slightly from 8.9% during the DB period to 10.5% during the DB+OL period; the incidence of discontinuation of PBO due to AEs during the DB period was 8.7%. Conclusions: With longer treatment exposure, DARO remained well-tolerated. In the DB+OL period, no new safety signals were observed. The expected increases in incidence of AEs between the DB and DB+OL periods largely disappeared when adjusted for the longer exposure, confirming the favorable safety profile of DARO with prolonged treatment. Clinical trial information: NCT02200614.

Analysis of the effect of crossover from placebo (PBO) to darolutamide (DARO) on overall survival (OS) benefit in the ARAMIS Trial

240

Background: DARO is a structurally distinct androgen receptor inhibitor approved for the treatment of non-metastatic castration-resistant prostate cancer (nmCRPC) based on significantly prolonged metastasis-free survival compared with PBO (median 40.4 vs 18.4 months; hazard ratio [HR] 0.41; 95% confidence interval [CI] 0.34–0.50; P < 0.0001) and a favorable safety profile in the phase III ARAMIS trial. Following unblinding at the primary analysis, crossover from PBO to DARO was permitted for the subsequent open-label treatment phase. Sensitivity analyses were performed to assess the effect of PBO–DARO crossover on OS benefit. Methods: Patients (pts) with nmCRPC receiving androgen deprivation therapy were randomized 2:1 to DARO (n = 955) or PBO (n = 554). In addition to OS, secondary endpoints included times to pain progression, first cytotoxic chemotherapy, first symptomatic skeletal event, and safety. The OS analysis was planned to occur after approximately 240 deaths, and secondary endpoints were evaluated in a hierarchical order. Iterative parameter estimation (IPE) and rank-preserving structural failure time (RPSFT) analyses were performed as pre-planned sensitivity analyses to adjust for the treatment effect of PBO–DARO crossover. The IPE method used a parametric model for the survival times and iteratively determined the model parameter describing the magnitude of the treatment effect, whereas a grid search and non-parametric log-rank test were used for the RPSFT analysis. The IPE and RPSFT analyses both generated a Kaplan–Meier curve for the PBO arm that predicts what would have been observed in the absence of PBO–DARO crossover. Results: After unblinding, 170 pts (30.7% of those randomized to PBO) crossed over from PBO to DARO; median treatment duration from unblinding to the final data cut-off was 11 months. Final analysis of the combined double-blind and open label periods was conducted after 254 deaths (15.5% of DARO and 19.1% of PBO pts) and showed a statistically significant OS benefit for DARO vs PBO (HR 0.69; 95% CI 0.53–0.88; P = 0.003). Results from the IPE (HR 0.66; 95% CI 0.51–0.84; P < 0.001) and RPSFT (HR 0.68; 95% CI 0.51–0.90; P = 0.007) analyses were similar to those from the intention-to-treat population, showing that the impact of PBO–DARO crossover was small. Additional analyses accounting for the effect of PBO–DARO crossover will be presented. The safety profile of DARO continued to be favorable at the final analysis, and discontinuation rates at the end of the double-blind period remained unchanged from the primary analysis (8.9% with DARO and 8.7% with PBO). Conclusions: Early treatment with DARO in men with nmCRPC is associated with significant improvement in OS regardless of pts crossing over from PBO to DARO. The safety profile of DARO remained favorable at the final analysis. Clinical trial information: NCT02200614.

CYCLONE 2: A phase II, randomized, placebo-controlled study of abiraterone acetate plus prednisone with or without abemaciclib in patients with metastatic castration-resistant prostate cancer

TPS5591

Background: Despite recent advances, nearly all patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) experience disease progression and cancer-specific mortality. Persistent or reactivated androgen receptor (AR) signaling and/or activation of pathways in cross-talk with AR signaling are key drivers of mCRPC progression. Evidence suggests that AR signaling promotes translation of D-type cyclins resulting in cyclin-dependent kinase 4 and 6 (CDK4&6) activation and cell cycle progression. Abemaciclib is an oral selective inhibitor of CDK4&6 dosed on a continuous schedule, that is FDA-approved in combination with endocrine therapy or as monotherapy to treat HR+, HER2- metastatic breast cancer pts. Preclinical studies with prostate cancer cell lines and xenograft models showed that abemaciclib induces cell cycle arrest and tumor growth inhibition. The hypothesis is that addition of abemaciclib to AR targeted therapy may be an effective treatment for mCRPC pts. Methods: CYCLONE 2 (NCT03706365) is a phase II, randomized, double-blind, multicenter, placebo-controlled study to assess the safety and efficacy of abemaciclib in combination with abiraterone acetate plus prednisone (AA+P) as first-line treatment of pts with mCRPC. The study is designed in two parts. Part 1 is a 30-patient safety lead-in to determine the recommended phase II dose (RP2D; 150 mg or 200 mg, twice daily) of abemaciclib in combination with AA (1000 mg, once daily) + P (5 mg, twice daily). In part 2, 150 pts are randomized 1:1 to abemaciclib at the RP2D with AA+P or placebo with AA+P. Pts who received prior AA+P, enzalutamide, apalutamide, darolutamide, radiopharmaceuticals, or sipuleucel-T are excluded. Prior docetaxel for metastatic hormone-sensitive prostate cancer, but not for mCRPC, is allowed. Pts must have progressive mCRPC (by PSA and/or imaging) and an accessible metastatic lesion for tumor biopsy. The co-primary objectives are radiographic PFS (per RECIST1.1 for soft tissue and PCWG3 for bone) and time to PSA progression. Secondary objectives include safety, objective response rate, duration of response, OS, time to symptomatic progression, and pharmacokinetics. Assuming hazard ratios of 0.64 (rPFS) and 0.6 (PSA progression), the study is powered to 80% and 85%, respectively, to test the superiority of abemaciclib plus AA+P vs. placebo plus AA+P at one-sided α=0.1 using stratified log-rank tests. Part 1 is completed and part 2 is enrolling in 70 sites worldwide. Clinical trial information: NCT03706365 .

Overall survival (OS) results of phase III ARAMIS study of darolutamide (DARO) added to androgen deprivation therapy (ADT) for nonmetastatic castration-resistant prostate cancer (nmCRPC)

5514

Background: DARO is a structurally distinct androgen receptor inhibitor with a favorable safety profile, approved for treating men with nmCRPC after demonstrating significantly prolonged metastasis-free survival, compared with placebo (PBO), in the phase III ARAMIS trial: median 40.4 vs 18.4 months, respectively (HR 0.41; 95% CI 0.34–0.50; P<0.0001). We report final analyses of OS and prospectively collected, patient-relevant secondary endpoints, and updated safety results. Methods: 1509 patients (pts) with nmCRPC were randomized 2:1 to DARO 600 mg twice daily (n=955) or PBO (n=554) while continuing ADT. Secondary endpoints included OS, and times to pain progression, first cytotoxic chemotherapy, and first symptomatic skeletal event. The OS analysis was planned to occur after approximately 240 deaths. Secondary endpoints were evaluated in a hierarchical order. Results: Final analysis was conducted after 254 deaths were observed (15.5% of DARO and 19.1% of PBO patients). After unblinding at the primary analysis, 170 pts crossed over from PBO to DARO. DARO showed a statistically significant OS benefit corresponding to a 31% reduction in the risk of death compared with placebo. All other secondary endpoints were significantly prolonged by DARO (Table), regardless of the effect of crossover and subsequent therapies on survival benefit. Incidences of treatment-emergent adverse events (AEs) with ≥5% frequency were generally comparable between DARO and PBO, similar to the safety profile observed at the primary analysis. Incidences of AEs of interest (including falls, CNS effects, and hypertension) were not increased with DARO compared with PBO when adjusted for treatment exposure. AEs in the crossover group were consistent with those for the DARO treatment arm. Conclusions: DARO showed a statistically significant OS benefit for men with nmCRPC. In addition, DARO delayed onset of cancer-related symptoms and subsequent chemotherapy, compared with PBO. With extended follow-up, safety and tolerability were favorable and consistent with the primary ARAMIS analysis (Fizazi et al, N Engl J Med 2019;380:1235-46). Clinical trial information: NCT02200614 .[Table: see text]

Prostate-specific antigen (PSA) kinetics in patients (pts) with advanced prostate cancer treated with apalutamide: Results from the TITAN and SPARTAN studies

5541

Background: The phase III TITAN and SPARTAN studies demonstrated improved outcomes with the addition of apalutamide (APA) to androgen deprivation therapy (ADT); outcomes included prolonging overall survival and radiographic progression-free survival (rPFS) in metastatic castration-sensitive prostate cancer (mCSPC) in TITAN, and metastasis-free survival (MFS) in nonmetastatic castration-resistant PC (nmCRPC) in SPARTAN. A post hoc analysis of PSA kinetics in pts from both studies is reported. Methods: Baseline PSA at randomization, time to PSA nadir, and proportion of pts achieving a PSA decline of ≥ 90% (PSA90) and of pts achieving a PSA ≤ 0.2 ng/mL at 3 and 12 months and at any time after treatment in the APA arms of the TITAN and SPARTAN studies were evaluated. Within each study, rPFS/MFS were compared between pts achieving a PSA90 or PSA ≤ 0.2 ng/mL response vs not. Results: 525 TITAN pts and 806 SPARTAN pts treated with APA were included in the analysis. Median baseline PSA, time to PSA nadir, median PSA nadir, and maximum percentage changes from baseline PSA are shown in the table. PSA90 and confirmed PSA ≤ 0.2 ng/mL were evident as early as 3 months in both TITAN and SPARTAN, and percentage of confirmed response continued to increase at 12 months. Pts treated with APA who achieved PSA90 were at lower risk of rPFS events in TITAN and of MFS events in SPARTAN, with a hazard ratio (95% confidence interval) of 0.46 (0.321-0.653) and 0.36 (0.271-0.489) in each respective study (both p < 0.0001), compared with APA pts who did not achieve PSA90. Pts with confirmed PSA ≤ 0.2 ng/mL had similar rPFS and MFS benefits. Conclusions: Pts with advanced PC, whether mCSPC or nmCRPC, treated with APA + ADT demonstrated rapid PSA declines that continued over time. There was a high rate of pts with PSA90 and with PSA ≤ 0.2 ng/mL responses, with a majority of pts reaching PSA90 by 12 months. Pts achieving PSA90 and/or PSA nadir of ≤ 0.2 ng/mL had a prolonged rPFS and MFS in TITAN and SPARTAN, respectively. Clinical trial information: NCT02489318; NCT01946204 . [Table: see text]

Association of detectable levels of circulating tumor DNA (ctDNA) with disease burden in prostate cancer (PC)

5562

Background: PC is characterized by a relatively low prevalence of recurrent somatic point mutations. ctDNA is shed from PC and can be analyzed to profile somatic point mutations and copy number changes. We evaluated a computational approach to detect ctDNA (ie. ctDNA+) in PC based on allele frequencies of polymorphisms and mutations. We then sought to confirm the association of this biomarker with disease burden and clinical outcome. Methods: Customized, hybrid capture, high-depth next-generation sequencing was performed on pre-treatment (PT) plasma samples from a phase 2 line 3+ metastatic castration-resistant PC (mCRPC) study (NCT02854436, GALAHAD) and PT and end of treatment (EOT) samples from randomized Phase 3 study in non-metastatic (nm) CRPC (NCT01946204, SPARTAN) and from metastatic castration-sensitive PC (mCSPC) (NCT02489318, TITAN). Associations of ctDNA+ with bone lesions (number), visceral metastases (+/-), circulating tumor cells count (CTCc), and serum prostate specific antigen (PSA), alkaline phosphatase (AP) and lactate dehydrogenase (LD) were tested. Also, associations of ctDNA+ with overall survival (OS) and second progression free survival (PFS2) were evaluated in randomized studies using Cox regression. Results: ctDNA+ at PT was 7.5% in nmCRPC, 23.7% in mCSPC and 66% in heavily pre-treated mCRPC. ctDNA+ increased from PT to EOT in nmCRPC (7.5% to 27%) and mCSPC (23.7% to 63.6%). Disease burden metrics were evaluated in ctDNA+ vs ctDNA- patients. ctDNA+ was associated with higher disease burden in mCRPC (Table), nmCRPC and mCSPC. At EOT, ctDNA+ patients had shorter OS and PFS2 in nmCRPC (HR [95% CI] OS: 2.73 [1.83, 4.08], p < 0.0001; PFS2: 2.00 [1.38, 2.90], p = 0.0002) and mCSPC (HR [95% CI] OS: 7.59 [3.22, 17.91], p < 0.0001; PFS2: 4.84 [2.47, 9.47], p < 0.0001). Conclusions: ctDNA+ assessed using our novel, composite biomarker increases with advanced disease state and disease progression, is significantly associated with disease burden and poor clinical outcome in PC and could be a clinically relevant metric for monitoring response to therapy. Clinical trial information: NCT02854436 . [Table: see text]

Molecular determinants of prostate specific antigen (PSA) kinetics and clinical response to apalutamide (APA) in patients (pts) with nonmetastatic castration-resistant prostate cancer (nmCRPC) in SPARTAN

5521

Background: In SPARTAN, APA + androgen deprivation therapy (ADT) prolonged metastasis-free survival (MFS) and improved PSA kinetics over placebo (PBO) + ADT in high-risk nmCRPC. All molecular subtypes derived benefit in MFS from APA (Feng FY, et al. ASCO GU 2019; abstract 42). We evaluated the association of PSA decline and efficacy outcomes in SPARTAN pts with different molecular subtypes. Methods: Gene expression from archival primary tumors (biomarker population) was assessed with the DECIPHER platform (Decipher Biosciences, Inc.) and stratified into genomic classifier (GC) high- and low-to-average risk using GC score > 0.6 and ≤ 0.6, respectively, and ADT-resistant or -sensitive basal or luminal A/B (PAM50 classifier) subtypes. PSA nadir and confirmed PSA decline (Table) were assessed in APA pts overall and at 3, 6, and 12 mo. Associations between molecular subtypes and outcomes were assessed. Results: Of 233 available samples, 154 were from APA pts; 49% of APA pts had high GC score and 66% had basal subtype. PSA levels at baseline were similar across all subtypes. Regardless of GC score or basal/luminal subtype, > 50% of patients achieved ≥ 90% reduction in PSA with APA. PSA declined faster and PSA reduction was deeper at 6 mo (Table) in GC low to average vs GC high risk and luminal vs basal subtypes. Overall, only luminal vs basal subtypes had a significantly higher % of pts with ≥ 90% PSA decline (Chi square p = 0.037). In luminal pts, deeper PSA decline with APA was consistent with improved MFS vs basal pts. In GC high pts, MFS benefit with APA was similar to that in GC low to average pts despite lower PSA decline. Although GC low to average and luminal pts had more rapid and deeper PSA responses than GC high or basal pts, respectively, all pts derived MFS benefit. Association of long-term outcomes with PSA decline in these molecular subtypes will be presented. Conclusions: In SPARTAN, all molecular subtypes of pts with nmCRPC treated with APA + ADT had MFS benefit and rapid and sustained PSA decline. PSA responses were deepest and most rapid in GC low to average and luminal subtypes. Clinical trial information: NCT01946204 . [Table: see text]

A phase II trial of cabozantinib in hormone receptor-positive breast cancer with bone metastases

1062

Background: We assessed the antitumor activity of cabozantinib, a potent multi-receptor oral tyrosine kinase inhibitor with activity against MET, RET, VEGFR2, and AXL, in patients with hormone-receptor positive (HR+) breast cancer with bone metastases. Methods: In this single-arm multicenter phase II study, patients with HR+, HER2- metastatic breast cancer and ≥ 1 prior line of therapy received an initial starting dose of 100 mg cabozantinib, later reduced to 60 mg per day. The primary endpoint was bone scan response rate determined by independent central review and defined as percent change of bone scan area from baseline. The target bone scan response rate was 30% compared to a null response rate of 10%. Secondary endpoints included objective response rate (ORR) by RECIST v1.1, progression free (PFS) and overall survival (OS). Bone scan and CT were obtained every 12 weeks. Results: Among 52 enrolled patients, median age was 55, and 54% and 42% had > 2 lines prior endocrine and chemotherapy, respectively and 18 (35%) had bone-only disease. 20 (38%) experienced a partial bone scan response and 6 (12%) had stable disease (SD). 16 (31%) patients discontinued study prior to week 12 assessment for early clinical progression or toxicity, and three (6%) had missing follow-up scans. Best extra-osseous overall response revealed SD in 26 (50%), but no objective responses. In 25 patients with bone scan disease control at 12 weeks, only 3 (12%) developed extra-osseous progression. Median PFS was 4.3 months (90% CI 2.8 - 5.5) and OS was 19.6 months (90% CI 18.0 – 26.8). In a landmark analysis, patients with bone scan disease control at 12 weeks had longer OS (median 24.2 months, 90% CI 16.4 – 31.7) than those without (median OS 13.3 months, 90% CI 9.5 – 18.2), with a hazard ratio of 0.37 (90% CI 0.21 – 0.65). Most common grade 3 or 4 toxicities were hypertension (10%), anorexia (6%), diarrhea (6%), fatigue (4%) and hypophosphatemia (4%). Dose reduction or delay occurred in 42 (81%) patients. Conclusions: This study met its primary endpoint with bone scans improved in 38% of patients with metastatic HR+ breast cancer and remained stable in an additional 12% with cabozantinib treatment. Bone scan response correlated with improved OS. This is the first reported study in breast cancer to use bone scan response as a primary endpoint. Further studies with cabozantinib in HR+ breast cancer and additional validation of bone scan response as a surrogate for clinical benefit in breast cancer are warranted. Clinical trial information: NCT01441947 .

A phase III randomized, placebo-controlled, double-blind study of niraparib plus abiraterone acetate and prednisone versus abiraterone acetate and prednisone in patients with metastatic prostate cancer (MAGNITUDE)

TPS5588

Background: Preclinical data suggest synergistic antitumor activity when the PARP inhibitor (PARPi) niraparib is combined with the androgen pathway inhibitor abiraterone acetate1. The addition of a PARPi to abiraterone acetate plus prednisone (AAP) showed improved radiographic progression-free survival (rPFS) vs AAP alone in patients with mCRPC regardless of DNA repair gene defect (DRD) status2. Interim results from a phase I study support safety and tolerability of niraparib 200 mg combined with AAP in patients with mCRPC3. The objective of this Phase III study is to compare the efficacy and safety of niraparib plus AAP versus AAP with placebo as first-line therapy for mCRPC. Methods: This ongoing multicenter MAGNITUDE study (NCT03748641) will open in approximately 300 sites across 28 countries and will enroll patients with mCRPC who have not received treatment in the metastatic castrate resistant setting other than ongoing androgen deprivation therapy [ADT] and ≤4 months of AAP. DRD status will be determined by plasma and tissue assays. The cohort with DRD (n=400) and the cohort without DRD (n=600) will each be randomized 1:1 to niraparib + AAP or placebo + AAP. The first patient was consented in February 2019 and enrollment is ongoing. The primary objective of the study is to compare radiographic progression-free survival (rPFS) as assessed by blinded independent central radiology review in each cohort and treatment group. To test superiority of the combination vs AAP, sample sizes were estimated to provide 92% power to detect HR≤0.65 rPFS in the cohort with DRD and 94% power to detect HR≤0.67 in rPFS in the cohort without DRD, both at a 2-tailed level of significance of 0.05. The secondary objectives are time to symptomatic progression, time to cytotoxic chemotherapy, and overall survival. Safety and pharmacokinetic profiles will be evaluated. 1Rajendra N, et al. Cancer Res 2019;79(13 Suppl):Abstract nr 2134. 2Clarke N, et al. Lancet Oncol. 2018;(7):975-986. 3Saad, et al. Ann Oncol, 2018;29 (suppl 8), mdy284.043, https://doi.org/10.1093/annonc/mdy284.043 ) Clinical trial information: NCT03748641 .

Final survival results from SPARTAN, a phase III study of apalutamide (APA) versus placebo (PBO) in patients (pts) with nonmetastatic castration-resistant prostate cancer (nmCRPC)

5516

Background: SPARTAN evaluated APA vs PBO in pts with nmCRPC and a prostate-specific antigen doubling time of ≤ 10 mo receiving androgen deprivation therapy (ADT). At primary end point analysis of metastasis-free survival (MFS), APA significantly improved median MFS by 2 yrs, as well as time to metastasis, progression-free survival, and time to symptomatic progression vs PBO (Smith, et al. NEJM 2018); overall survival (OS) results were immature. SPARTAN was unblinded upon meeting the primary end point; pts still on PBO were allowed to cross over to APA. Final survival results are reported herein. Methods: 1207 nmCRPC pts were randomized 2:1 to APA (240 mg QD) or PBO plus ongoing ADT. At progression, pts could receive open-label sponsor-provided abiraterone acetate + prednisone. After the primary efficacy end point (MFS) was met, 76 PBO pts (19%) crossed over to APA. OS and time to cytotoxic chemotherapy (TTCx) were tested by group sequential testing procedure with O’Brien-Fleming (OBF)-type alpha spending function. Time-to-event end points were analyzed by Kaplan-Meier method and Cox model. A sensitivity analysis for OS, accounting for crossover using a naïve censoring approach, was conducted. Results: With follow-up of 52.0 mo, 428 (of 427 required) OS events had occurred. Median treatment duration: APA, 32.9 mo; PBO, 11.5 mo. Median OS was significantly longer with APA + ADT vs PBO + ADT (73.9 vs 59.9 mo), (hazard ratio [HR], 0.784, Table). APA significantly lengthened TTCx (HR, 0.629). Discontinuation rates (APA vs PBO) due to progressive disease were 42.7% vs 73.9%, and due to adverse events (AE) 15.2% vs 8.4%. Safety was consistent with previous reports; grade 3/4 treatment-emergent (TE) AEs of special interest were rash 5.2%, fractures 4.9%, falls 2.7%, ischemic heart disease 2.6%, hypothyroidism 0%, and seizures 0%. 1 TEAE leading to death (myocardial infarction) was considered potentially APA related. Conclusions: In pts with nmCRPC, APA + ADT significantly improved OS compared with PBO + ADT, with median OS > 6 yr in the APA + ADT group and 14 mo improvement over PBO + ADT. Benefit from APA was observed despite a 19% crossover from PBO. The safety profile of APA was consistent with prior interim analyses. Clinical trial information: NCT01946204 . [Table: see text]

Niraparib in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) and biallelic DNA-repair gene defects (DRD): Correlative measures of tumor response in phase II GALAHAD study

118

Background: Niraparib, a highly potent and selective poly (ADP-ribose) polymerase inhibitor (PARPi) received breakthrough designation by US FDA for treatment of pts with BRCA1,2 mutant mCRPC who progressed on taxane and androgen receptor-targeted therapy. Circulating tumor cells (CTC) detection associates with poor outcomes, with declining counts consistent with improved survival [1,2]. Methods: GALAHAD study assessed niraparib (300 mg daily) in pts with mCRPC+DRD (NCT02854436). Patients with non-measurable soft tissue disease by RECIST 1.1 were required to have a baseline CTC count ≥1 cell/7.5 mL blood. CTC response was defined as CTC conversion to <5 for pts with baseline CTC≥5 and CTC drop to 0 post-baseline for pts with ≥1 baseline CTC. Alkaline phosphatase (ALP) was collected at each monthly cycle. Results: For primary efficacy population of pts with BRCA1/2 mutations, the objective response rate (ORR) by RECIST 1.1 criteria was 41.4%. CTC response rates for this population were as high as ORR regardless of measurability (Table). Time to CTC response for each CTC responder will be shown. Radiographic progression-free survival (rPFS) durations were similar for patients with a measurable disease response and patients with CTC conversion. Median duration of treatment for responders of any type was 6.7mo (range: 2–27). DRD status, both BRCA and non- BRCA, for each responder will also be discussed. Trends in disease burden and markers of bone metabolism will also be quantitatively explored including 24% pts who were on treatment for at least one cycle who had ≥25% decreased unfractionated ALP from baseline. Conclusions: Niraparib showed clinical activity with CTC response and decline in ALP levels in mCRPC pts having biallelic BRCA mutations, which further supports its recent breakthrough designation. Clinical trial information: NCT02854436. [Table: see text]

Clinical outcomes and patient (pt) profiles in REASSURE: An observational study of radium-223 (Ra-223) in metastatic castration-resistant prostate cancer (mCRPC)

32

Background: Ra-223 is a targeted alpha therapy that showed a survival advantage and favorable safety profile in the phase 3 ALSYMPCA trial in pts with mCRPC. REASSURE (NCT02141438) is evaluating the long-term safety of Ra-223 in routine clinical practice in pts with mCRPC over a 7-year follow-up period. Methods: In this global, prospective, single-arm, observational study, the second prespecified interim analysis (data cut-off March 2019) evaluated safety and clinical outcomes of Ra-223 in pts with mCRPC. Primary outcome measures were incidence of second primary malignancies (SPM), bone marrow suppression and short- and long-term safety in pts who had ≥1 Ra-223 dose. Secondary outcomes included overall survival (OS). Results: For 1465 pts in the safety analysis, median follow up was 11.5 months. Median PSA (n=1053), ALP (n=1048), and LDH (n=555) levels at baseline were 59 ng/mL, 135 U/L, and 269 U/L, respectively. 81% of pts had bone metastases only at baseline; 19% of pts had other metastatic sites, mostly in the lymph nodes. 19% of pts had <6 metastatic sites, 47% had 6–20 sites, 20% had >20 lesions but not a superscan, and 6% had a superscan. 45%, 38%, 37%, 9%, and 8% of pts received prior abiraterone, docetaxel, enzalutamide, cabazitaxel, or sipuleucel-T as prior therapies, respectively. Median number of Ra-223 doses received was 6; 67% of pts had ≥5 doses. SPM occurred in 1% of pts. The most common treatment-emergent drug-related adverse event (AE) of any grade was diarrhea (11%). 10% of pts had a bone-associated event, 5% had fractures, and 15% had a hematological AE. Median OS was 15.6 months (95% CI 14.6–16.5). Conclusions: In REASSURE, there was a low incidence of SPM, bone fractures, and bone marrow suppression after Ra-223 treatment, with no new AEs identified. This study confirms that in routine clinical practice, Ra-223 AE rates were low, and pts generally received ≥5 doses. Clinical trial information: NCT02141438. [Table: see text]

A phase III randomized, placebo-controlled, double-blind study of niraparib plus abiraterone acetate and prednisone versus abiraterone acetate and prednisone in patients with metastatic prostate cancer (NCT03748641)

TPS257

Background: Preclinical data suggest synergistic antitumor activity when the PARP inhibitor (PARPi) niraparib is combined with the androgen pathway inhibitor abiraterone acetate. (1) The addition of a PARPi to abiraterone acetate plus prednisone (AAP) showed improved radiographic progression-free survival (rPFS) vs AAP alone in patients with mCRPC regardless of DNA repair gene defect (DRD) status. (2) Interim results from a phase 1 study support safety and tolerability of niraparib 200 mg combined with AAP in patients with mCRPC. (3) The objective of this Phase 3 study is to compare the efficacy and safety of niraparib plus AAP versus AAP with placebo as first-line therapy for mCRPC. Methods: This ongoing multicenter MAGNITUDE study will open in 300 sites across 28 countries and will enroll patients with mCRPC who have not received treatment in the metastatic castrate resistant setting other than ongoing androgen deprivation therapy [ADT] and ≤4 months of AAP. The DRD positive cohort (Cohort 1, n=400) will comprise patients whose tumors have DRD, as determined by a previously validated plasma or tissue assay. The cohort without DRD (Cohort 2, n=600) will enroll patients whose tumors are not found to have DRD. Enrollment began in February 2019. The primary objective of the study is to compare radiographic progression-free survival (rPFS) as assessed by blinded independent central radiology review for patients treated with niraparib and AAP versus placebo and AAP. To test superiority of the combination vs AAP, sample sizes were estimated to provide 92% power to detect HR≤0.65 rPFS in the DRD positive cohort and 94% power to detect HR≤0.67 in rPFS in the cohort without DRD, both at a 2-tailed level of significance of 0.05. The main secondary objectives are time to symptomatic progression, time to cytotoxic chemotherapy, and overall survival. Safety and pharmacokinetic profiles will be evaluated.1) Rajendra N, et al. Cancer Res 2019;79 (13 Suppl): Abstract nr 2134. 2) Clarke N, et al. Lancet Oncol. 2018;(7):975-986. 3) Saad, et al. Ann Oncol, 2018;29 (suppl 8), mdy284.043, https://doi.org/10.1093/annonc/mdy284.043 ). Clinical trial information: NCT03748641.

Apalutamide and overall survival in non-metastatic castration-resistant prostate cancer

BACKGROUND

In the SPARTAN study, compared with placebo, apalutamide added to ongoing androgen deprivation therapy significantly prolonged metastasis-free survival (MFS) and time to symptomatic progression in patients with high-risk non-metastatic castration-resistant prostate cancer (nmCRPC). Overall survival (OS) results at the first interim analysis (IA1) were immature, with 104 of 427 (24%) events required for planned final OS analysis. Here, we report the results of a second pre-specified interim analysis (IA2).

METHODS

One thousand two hundred and seven patients with nmCRPC were randomized 2 : 1 to apalutamide (240 mg daily) or placebo. The primary end point of the study was MFS. Subsequent therapy for metastatic CRPC was permitted. When the primary end point was met, the study was unblinded. Patients receiving placebo who had not yet developed metastases were offered open-label apalutamide. At IA2, pre-specified analysis of OS was undertaken, using a group-sequential testing procedure with O'Brien-Fleming-type alpha spending function. Safety and second progression-free survival (PFS2) were assessed.

RESULTS

Median follow-up was 41 months. With 285 (67% of required) OS events, apalutamide was associated with an improved OS compared with placebo (HR 0.75; 95% CI 0.59-0.96; P = 0.0197), although the P-value did not cross the pre-specified O'Brien-Fleming boundary of 0.0121. Apalutamide improved PFS2 (HR 0.55; 95% CI 0.45-0.68). At IA2, 69% of placebo-treated and 40% of apalutamide-treated patients had received subsequent life-prolonging therapy for metastatic CRPC. No new safety signals were observed.

CONCLUSION

In patients with nmCRPC, apalutamide was associated with a 25% reduction in risk of death compared with placebo. This OS benefit was observed despite crossover of placebo-treated patients and higher rates of subsequent life-prolonging therapy for the placebo group.

Bacterial community structure and response to nitrogen amendments in Lake Shenandoah (VA, USA)

Microbial processes are critical to the function of freshwater ecosystems, yet we still do not fully understand the factors that shape freshwater microbial communities. Furthermore, freshwater ecosystems are particularly susceptible to effects of environmental change, including influx of exogenous nutrients such as nitrogen and phosphorus. To evaluate the impact of nitrogen loading on the microbial community structure of shallow freshwater lakes, water samples collected from Lake Shenandoah (Virginia, USA) were incubated with two concentrations of either ammonium, nitrate, or urea as a nitrogen source. The potential impact of these nitrogen compounds on the bacterial community structure was assessed via 16S rRNA amplicon sequencing. At the phylum level, the dominant taxa in Lake Shenandoah were comprised of Actinobacteria and Proteobacteria, which were not affected by exposure to the various nitrogen treatments. Overall, there was not a significant shift in the diversity of the bacterial community of Lake Shenandoah with the addition of nitrogen sources, indicating this shallow system may be constrained by other environmental factors.

The use of the Körperkoordinationstest für Kinder in the talent pathway in youth athletes: A systematic review

OBJECTIVES

Identifying talented athletes from an early age to accelerate their development requires the investment of substantial resources. Due to the need for multifactorial approaches to talent identification, motor competence assessments are increasingly prevalent in contemporary testing batteries. Therefore, the aim of this review was to evaluate the literature on the use of a product-oriented motor competence assessment tool, the Körperkoordinationstest für Kinder (KTK) in the talent pathway and determine whether it is warranted in such programs.

METHODS

Three electronic databases (i.e. PubMed, SPORTDiscus and Web of Science) were searched for studies that used at least one component of the KTK to assess motor competence for talent detection, identification, development and selection in athletic populations. A total of 21 articles were included in the review, of which seven used the full version of the KTK and 14 used modified versions or individual components of the battery. The quality of included studies was assessed using a modified version of the Joanna Brigg's Institute Critical Appraisal Checklist.

RESULTS

The analysed literature suggests that the KTK can successfully distinguish between athletes of different competition levels and across different sporting domains, however, findings should be interpreted with caution due to the cross-sectional nature of the studies. Furthermore, the moving sideways subtest displayed the greatest discriminative power for athletes of different competition levels. Motor competence was not affected by maturation and did not differ between genders or playing positions.

CONCLUSIONS

Collectively, these findings suggest that the KTK is a useful motor competence assessment in the talent pathway.

Impact of darolutamide (DARO) on pain and quality of life (QoL) in patients (Pts) with nonmetastatic castrate-resistant prostate cancer (nmCRPC)

5000

Background: DARO is a structurally distinct androgen receptor antagonist for which in vitro and phase 1/2 studies suggest low risk of adverse events (AEs) and drug–drug interaction. In the ARAMIS study of DARO in nmCRPC, metastasis-free survival (MFS) was significantly prolonged vs placebo (PBO) (40.4 vs 18.4 mo; hazard ratio [HR] 0.41; 95% confidence interval [CI] 0.34–0.50; P < 0.001) and interim overall survival (OS) favored DARO (HR 0.71; 95% CI 0.50–0.99; P = 0.045). Methods: 1509 pts were randomized 2:1 to DARO 600 mg (two 300 mg tablets) twice daily (n = 955) or PBO (n = 554) while continuing androgen deprivation therapy (ADT). Primary endpoint was MFS. Secondary endpoints included OS and time to pain progression (assessed by Brief Pain Inventory Short Form). QoL was assessed by European Organisation for Research and Treatment of Cancer QoL Prostate Cancer module (EORTC-QLQ-PR25) at baseline (BL) and every 16 wks until end of treatment. Analysis of time to deterioration in EORTC-QLQ-PR25 subscales, defined as first occurrence of a minimally important difference (half the standard deviation of BL value), used Kaplan–Meier estimators and stratified Cox proportional hazard models. Results: DARO significantly delayed pain progression vs PBO (40.3 vs 25.4 mo; HR 0.65; 95% CI 0.53–0.79; P < 0.001); this was maintained beyond end of study treatment. Time to deterioration of EORTC-QLQ-PR25 outcomes showed statistically and clinically significant delays with DARO vs PBO for urinary symptoms (25.8 vs 14.8 mo; HR 0.64; 95% CI 0.54–0.76; P < 0.01). Time to deterioration of hormonal treatment-related symptoms was comparable with DARO vs PBO (18.9 vs 18.4 mo; HR 1.06; 95% CI 0.88–1.27; P = 0.52). DARO was well tolerated. Exposure-adjusted incidences (pts per 100 years’ exposure) of AEs of interest were similar/lower with DARO vs PBO (fatigue/asthenic conditions [11.3 vs 11.1], hypertension [4.7 vs 5.1], hot flush [3.7 vs 4.1], fracture [3.0 vs 3.5], falls [2.7 vs 4.1], cognitive disorder [0.3 vs 0.2], and seizure [0.2 vs 0.2]). Conclusions: For nmCRPC pts, DARO prolongs MFS, is well tolerated, maintains QoL, and delays worsening of pain and disease-related symptoms compared with PBO. Clinical trial information: NCT02200614.

Efficacy of apalutamide (APA) plus ongoing androgen deprivation therapy (ADT) in patients (pts) with nonmetastatic castration-resistant prostate cancer (nmCRPC) and baseline (BL) comorbidities (CM)

5023

Background: The addition of APA to ongoing ADT in pts with nmCRPC significantly prolonged metastasis-free survival (MFS), time to symptomatic progression (SymProg), and second progression-free survival (PFS2) in SPARTAN. We assessed the impact of APA on these end points in pts with or without BL CM. Methods: Using Cox proportional hazards models, treatment effect of APA was evaluated in SPARTAN pts with CM at BL, stratifying by the presence of BL diabetes/hyperglycemia (D/H), cardiovascular disease (CVD), hypertension (HTN), and renal insufficiency (RI). Results: Of 1207 SPARTAN pts, 1062 (88%) had ≥ 1 BL CM, including 703/806 (87%) APA pts and 359/401 (90%) PBO pts. A total of 226 (19%), 398 (33%), 798 (66%), and 774 (64%) pts had D/H, CVD, HTN, and RI, respectively; 323 (27%), 412 (34%), 259 (21%), and 68 (6%) pts had 1, 2, 3, and 4 CM, respectively. Incidence of CM was balanced between arms. Pts with CM were older than pts with no CM (median age, 75 vs 69 yrs, APA; 74 vs 69 yrs, PBO). MFS, SymProg, and PFS2 benefit with APA was significant in all CM subgroups, except PFS2 for pts with D/H (Table) and regardless of the number of CM. The incidence of any treatment-emergent AE was balanced between pts with and without CM. AEs with APA were not affected by any CM. Clinical trial information: NCT01946204. Conclusions: The benefit of APA + ongoing ADT in pts with nmCRPC was maintained in pts with D/H, CVD, HTN, and RI. The safety profile of APA was not affected by any CM.[Table: see text]

Predictors of falls and fractures in patients (pts) with nonmetastatic castration-resistant prostate cancer (nmCRPC) treated with apalutamide (APA) plus ongoing androgen deprivation therapy (ADT)

5025

Background: SPARTAN, a phase 3 study of APA vs placebo (PBO) added to ongoing ADT in pts with nmCRPC, demonstrated that APA significantly prolongs metastasis-free survival, time to symptomatic progression, and second progression free survival (Smith et al. NEJM 2018), with no decline in health-related quality of life (Saad et al. Lancet Oncol 2018). SPARTAN pts who received APA, vs PBO, with ongoing ADT had higher rates of falls (15.6% vs 9.0%) and fractures (11.7% vs 6.5%). An analysis was performed to identify clinical characteristics associated with falls and fractures in APA-treated SPARTAN pts. Methods: Of 1207 pts enrolled, 806 were randomized to APA. Univariate Cox proportional hazards model (UVA) assessed the association of 47 baseline clinical characteristics (demographics, comorbidities, and medication use, including bone-sparing agents) with time to fall or time to fracture. Characteristics with p values < 0.10 were included in a multivariate Cox proportional hazards model (MVA) to determine independent factors associated with these outcomes (p < 0.05). Results: Factors associated with time to both fall and fracture on UVA (p < 0.10) included older age, low serum albumin, and poor ECOG performance status (PS). Additional factors associated with time to fall were cerebrovascular accidents/transient ischemic attacks, neuropathy, depression, α-blocker use, and antidepressant use. On MVA, older age, poor ECOG PS, history of neuropathy, and α-blocker use were independently associated with falls; older age and low serum albumin were independently associated with fractures (Table). Conclusions: At initiation of APA added to ongoing ADT, nmCRPC pts with higher risk of falls and fractures can be identified and are candidates for intervention to reduce the risk for these events. Clinical trial information: NCT01946204. [Table: see text]

Age-related efficacy and safety of apalutamide (APA) plus ongoing androgen deprivation therapy (ADT) in subgroups of patients (pts) with nonmetastatic castration-resistant prostate cancer (nmCRPC): Post hoc analysis of SPARTAN

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Background: SPARTAN, a randomized phase 3 placebo (PBO)-controlled study in pts with high-risk nmCRPC and PSA doubling time ≤ 10 mo, showed that, compared with PBO, addition of APA to ongoing ADT treatment (tx) prolonged metastasis-free survival (MFS) by > 2 y, reduced the risk of symptomatic progression by 55%, and increased second progression-free survival (PFS2), which is the time from randomization to disease progression on first subsequent anticancer tx, or death. The impact of APA in terms of benefit and safety profile was evaluated in pts aged < 65, 65-74, and ≥ 75 y. Methods: Pts with nmCRPC were randomized 2:1 to APA (240 mg QD) or PBO; ADT was continuous. APA effect was analyzed by Cox models and Kaplan-Meier methods across age subgroups. Results: Baseline characteristics among age groups were similar, although ECOG PS 1 vs 0 increased with age. MFS benefit with APA was highly significant for all age subgroups (Table). In pts ≥ 75 y, MFS risk with APA vs PBO was reduced by 59%; MFS risk was reduced by 86% and 76% for pts < 65 and 65-74 y, respectively. Risk of PFS2 with APA vs PBO was reduced across all age subgroups. PFS2 in pts < 65, 65-74, and ≥ 75 y: HR, 0.09 (p < 0.0001); HR, 0.56 (p = 0.0343); HR, 0.59 (p = 0.0092), respectively. Risk of symptomatic progression was lessened with APA vs PBO for all age subgroups (Table). There was a similar increase in incidence of tx-emergent adverse events (TEAE) with age in both tx arms that remained higher with APA. Incidence of grade 3/4 TEAE (≥ 75 vs < 65 y): APA, 50% vs 37%; PBO, 37% vs 28%. Conclusions: Pts in all age subgroups with high-risk nmCRPC had significant improvement in MFS with APA + ongoing ADT. The safety profile of APA was similar across age subgroups. Clinical trial information: NCT01946204. [Table: see text]

Identifying molecular determinants of response to apalutamide (APA) in patients (pts) with nonmetastatic castration-resistant prostate cancer (nmCRPC) in the SPARTAN trial

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Background: The SPARTAN trial recently demonstrated that addition of APA to androgen deprivation therapy (ADT) improved metastasis-free survival (MFS) and second progression-free survival (PFS2) in nmCRPC pts. We performed transcriptome-wide profiling of available primary tumor samples from pts in SPARTAN to evaluate potential biomarkers of response or resistance to APA+ADT. Methods: Pts included in SPARTAN were at high risk of developing metastasis.We used a commercially available genomic assay (DECIPHER prostate test, GenomeDx Biosciences, Inc., San Diego, CA) to assess gene expression in 233 archived primary tumors from SPARTAN pts. Using a Cox proportional hazard model, we assessed the association between scores and subtypes from previously derived prognostic and predictive gene signatures, such as DECIPHER and basal (BA) vs luminal (LU) subtyping. Results: Pts with high DECIPHER scores had greater treatment effect with APA+ADT than those with low scores. Pts with LU, a subtype known to be sensitive to ADT, greatly benefited from APA+ADT. Pts with BA, typically resistant to ADT, also benefited from APA+ADT. Conclusions: DECIPHER score and BA or LU subtype may be biomarkers of response to APA+ADT. DECIPHER may be useful for identifying pts for early treatment intensification with APA or other agents, and molecular subtyping may be an effective approach for pt selection in trials combining novel therapies with APA. Clinical trial information: NCT01946204. [Table: see text]

ARAMIS: Efficacy and safety of darolutamide in nonmetastatic castration-resistant prostate cancer (nmCRPC)

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Background: Delaying metastases for nmCRPC patients, while minimizing the risk of adverse events, is an important treatment goal. Darolutamide, a structurally unique androgen receptor (AR) antagonist, is being evaluated for the treatment of advanced prostate cancer. The ARAMIS trial studied the efficacy and safety of darolutamide in nmCRPC patients. Methods: This double-blind, placebo-controlled phase III trial randomized nmCRPC patients in a 2:1 ratio to receive darolutamide 600 mg (two 300 mg tablets) twice-daily or placebo, while continuing androgen deprivation therapy. Patients were stratified by prostate-specific antigen doubling time (≤6 months or >6 months) and use of osteoclast-targeted therapy. The primary endpoint was metastasis-free survival (MFS), with independent central review of radiographic imaging every 16 weeks. Secondary endpoints include overall survival (OS), times to pain progression (assessed by Brief Pain Inventory), first cytotoxic chemotherapy and first symptomatic skeletal event, as well as safety profile. Results: In total, 1,509 patients were randomized (955 to darolutamide, 554 to placebo). Median MFS was 40.4 months with darolutamide vs 18.4 months with placebo (hazard ratio [HR] 0.41; 95% confidence interval [CI] 0.34–0.50; 2-sided p<0.0001). OS showed a trend in favor of darolutamide (HR 0.71, 95% CI 0.50–0.99, 2-sided p=0.045), as did time to pain progression (HR 0.65; 95% CI 0.53–0.79; 2-sided p<0.0001). Other secondary and exploratory efficacy endpoints also favored darolutamide. Incidences of treatment-emergent adverse events (AEs) with ≥5% frequency or grade 3–5 were comparable between darolutamide and placebo arms; none except fatigue occurred in >10%. Discontinuation rates due to AEs were 8.9% with darolutamide and 8.7% with placebo. Grouped terms for AEs noted with other AR inhibitors (including fracture, falls, seizures, weight decrease, hypertension, and cognitive disorder) showed minimal or no difference in incidence between study arms. Conclusion: Among men with nmCRPC, MFS was significantly longer with darolutamide than with placebo with a low incidence of treatment-related AEs in this asymptomatic patient population. Clinical trial information: NCT02200614.

Updated analysis of progression-free survival with first subsequent therapy (PFS2) and safety in the SPARTAN study of apalutamide (APA) in patients (pts) with high-risk nonmetastatic castration-resistant prostate cancer (nmCRPC)

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Background: In the phase 3 SPARTAN study, compared with placebo (PBO), APA, a next-generation androgen receptor inhibitor, decreased the risk of distant metastasis or death by 72% (hazard ratio [HR], 0.28; p < 0.0001) in men with high-risk nmCRPC. After 1 year of additional follow-up, PFS2 and safety were reevaluated to ensure maintenance of benefit against potential harm. Methods: Pts with nmCRPC and prostate-specific antigen doubling time of ≤ 10 mos were randomized 2:1 to APA (240 mg QD) + androgen deprivation therapy (ADT) or PBO + ADT. All pts who developed distant metastasis, determined by blinded independent central review, were eligible to receive subsequent therapy including open-label treatment with abiraterone acetate + prednisone, provided by the sponsor. The exploratory PFS2 end point (time from randomization to disease progression on subsequent anticancer therapy or death) was evaluated, as was incidence of treatment-emergent adverse events (TEAEs). Results: Median treatment duration with APA was 25.7 mos; with PBO, 11.5 mos (original analysis, mos: APA, 19.2; PBO, 11.2). Pts randomized to APA continued to show significant benefit in PFS2 (HR, 0.5; 95% CI, 0.39-0.63; p < 0.0001) vs PBO (APA median time to PFS2 not reached vs PBO 39.3 mos). At a median follow-up of 32 mos, 51.3% of pts receiving APA, 8% of the 75 pts who crossed over from PBO to APA, and 99.7% of remaining PBO pts had discontinued study treatment. Rates of discontinuations due to progressive disease and AEs were 27.3% and 12.7%, respectively, in the APA group and 73.4% and 8.4% in the PBO group. There was no substantial change in the incidence of TEAEs in the APA group at the 1-year update. With regard to drug specific TEAEs, there were no grade 4 or 5 events; grade 3 TEAEs consisted of rash, 5.2%; falls, 2.4%; fractures, 3.1%; hypothyroidism, 0%; and seizures, 0%. Conclusions: APA was previously shown to result in an improvement in metastasis-free survival and symptomatic progression. With a median APA treatment duration of 25.7 mos, APA continues to show significant benefit in PFS2, and its safety profile remains unchanged. Clinical trial information: NCT01946204.

Assessment of circulating tumor cell number as a transitional surrogate endpoint for survival in phase II trials for metastatic castration-resistant prostate cancer

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Background: Short-term measures of response that reflect clinical benefit are a critical unmet need for clinical trials for mCRPC. Using data from 5 randomized mCRPC trials, we showed that a response endpoint (RE) based on a change in CTC number using the FDA cleared CellSearch® (Menarini) platform from any, (≥ 1, CTC any) to 0 (CTC0) per 7.5 ml of blood was associated strongly with overall survival (OS). Here we explored whether different CTC and PSA REs could serve as “transitional surrogates” defined as a biomarker validated in phase 2 but not in phase 3 trials for overall survival (OS), using the baseline and week 13 prostate-specific antigen (PSA) level and CTC counts. Methods: Four 13-week REs were studied: (i) PSA50 (≥ 50% PSA decline from baseline), (ii) CTC0 (≥ 1 CTC/7.5 ml of blood at baseline and 0 CTCs at week 13), (iii) both PSA50 and CTC0, and (iv) either PSA50 or CTC0. The relative effectiveness of these REs as transitional surrogates for OS was evaluated at the patient level by discrimination, the separation between responder and non-responder survival curves, and at the trial level using explained variation, the accuracy in predicting k-month survival in a trial with the response proportion. Results: A total of 6081 pts were enrolled of whom 5660 (93%) survived until week 13 and among these patients 3080 (54%) had a baseline CTC count ≥ 1 and baseline PSA ≥ 5 ng/ml. At the patient level, separation between responder and non-responder survival curves over time was greater using CTC0 than PSA50 (average difference in survival probability 0.35 vs. 0.29, respectively). At the trial level, explained variation in survival over time was also greater for CTC0 than PSA50 (average R-squared 0.67 vs. 0.58, respectively). CTC/PSA combination REs did not improve on CTC0 at either level. Conclusions: The CTC0 RE provides stronger discrimination than PSA50 at the patient level and greater observed explained variation at the trial level. The results suggest that for the individual patient, a decrease in CTCs to zero at week 13 is a stronger indicator of longer term OS than the more widely used PSA50 and serves as a reasonably likely surrogate for OS in clinical trials.

Phase II study of niraparib in patients with metastatic castration-resistant prostate cancer (mCRPC) and biallelic DNA-repair gene defects (DRD): Preliminary results of GALAHAD

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Background: New therapies are needed for patients (pts) with mCRPC progressing after androgen-receptor signaling inhibitors (ARSIs) and taxane therapies. Niraparib is a once daily highly selective inhibitor of poly (ADP-ribose) polymerase (PARP-1 and 2). Methods: GALAHAD is an ongoing open label Ph 2 study assessing niraparib (300 mg daily) in pts with DRD progressing on/after ARSIs and taxane chemotherapy. Using a validated plasma assay, DRD status was defined as pathogenic mutations (including homozygous deletions) of BRCA1/2, ATM, FANCA, PALB2, CHEK2, BRIP1 or HDAC2. Composite response rate (RR) was defined as an objective response by RECIST 1.1 for measurable disease, circulating tumor cell (CTC) conversion to < 5/7.5 mL blood or prostate-specific antigen (PSA) decline of ≥50% (PSA50). Here, preliminary data on RR and adverse events (AEs) are reported in pts with biallelic DRD. Results: As of 10 Sep 2018, 123 pts with mCRPC and DRD were enrolled, of whom 39 had biallelic DRD (23 BRCA1/2). The median follow-up was 5.7 mo (2.0–23.7). Table depicts RRs for pts with biallelic DRD by BRCA status. Composite and objective RRs were 65% and 38% in pts with biallelic BRCA1/2, respectively. 3/8 pts (38% [2/5 BRCA1/2 and 1/3 non-BRCA]) with measurable visceral metastases showed objective response. Among the 20 biallelic responders, the duration of treatment (tx) has exceeded 4 mo in 13 pts and 6 mo in 8 pts; 14 pts remain on tx. The most common grade 3/4 hematologic AEs were anemia (25%) and thrombocytopenia (15%) (manageable by dose reduction/interruption). The most common grade 3/4 nonhematologic AEs were asthenia (6%) and hypertension (5%). Conclusions: These results suggest niraparib has compelling activity as monotherapy for pts with treatment-resistant mCRPC, particularly those with biallelic BRCA1/2 identified by a blood assay. Clinical trial information: NCT02854436. [Table: see text]

Androgen receptor mutations in patients with castration-resistant prostate cancer treated with apalutamide

Background

Mutations in the androgen receptor (AR) ligand-binding domain (LBD), such as F877L and T878A, have been associated with resistance to next-generation AR-directed therapies. ARN-509-001 was a phase I/II study that evaluated apalutamide activity in castration-resistant prostate cancer (CRPC). Here, we evaluated the type and frequency of 11 relevant AR-LBD mutations in apalutamide-treated CRPC patients.

Patients and methods

Blood samples from men with nonmetastatic CRPC (nmCRPC) and metastatic CRPC (mCRPC) pre- or post-abiraterone acetate and prednisone (AAP) treatment (≥6 months' exposure) were evaluated at baseline and disease progression in trial ARN-509-001. Mutations were detected in circulating tumor DNA using a digital polymerase chain reaction-based method known as BEAMing (beads, emulsification, amplification and magnetics) (Sysmex Inostics' GmbH).

Results

Of the 97 total patients, 51 had nmCRPC, 25 had AAP-naïve mCRPC, and 21 had post-AAP mCRPC. Ninety-three were assessable for the mutation analysis at baseline and 82 of the 93 at progression. The overall frequency of detected AR mutations at baseline was 7/93 (7.5%) and at progression was 6/82 (7.3%). Three of the 82 (3.7%) mCRPC patients (2 AAP-naïve and 1 post-AAP) acquired AR F877L during apalutamide treatment. At baseline, 3 of the 93 (3.2%) post-AAP patients had detectable AR T878A, which was lost after apalutamide treatment in 1 patient who continued apalutamide treatment for 12 months.

Conclusions

The overall frequency of detected mutations at baseline (7.5%) and progression (7.3%) using the sensitive BEAMing assay was low, suggesting that, based on this assay, AR-LBD mutations such as F877L and T878A are not common contributors to de novo or acquired resistance to apalutamide.

ClinicalTrials.gov identifier

NCT01171898.