Health-related quality of life in GALAHAD: A multicenter, open-label, phase 2 study of niraparib for patients with metastatic castration-resistant prostate cancer and DNA-repair gene defects

BACKGROUND: Niraparib is a highly selective poly (adenosine diphosphateribose) polymerase-1 and poly (adenosine diphosphate-ribose) polymerase-2 inhibitor indicated for select patients with ovarian, fallopian tube, and primary peritoneal cancer. The phase 2 GALAHAD trial (NCT02854436) demonstrated that niraparib monotherapy is tolerable and efficacious in patients with metastatic castration-resistant prostate cancer (mCRPC) and homologous recombination repair (HRR) gene alterations, particularly those with breast cancer gene (BRCA) alterations who had progressed on prior androgen signaling inhibitor therapy and taxane-based chemotherapy. OBJECTIVE: To report the prespecified patient-reported outcomes analysis from GALAHAD. METHODS: Eligible patients with alterations to BRCA1 and/or BRCA2 (BRCA cohort) and with pathogenic alterations in other HRR genes (other HRR cohort) were enrolled and received niraparib 300 mg once daily. Patient-reported outcome instruments included the Functional Assessment of Cancer Therapy-Prostate and the Brief Pain Inventory-Short Form. Changes from baseline were compared using a mixed-effect model for repeated measures. RESULTS: On average, health-related quality of life (HRQoL) improved in the BRCA cohort by cycle 3 (mean change = 6.03; 95% CI = 2.76-9.29) and was maintained above baseline until cycle 10 (mean change = 2.84; 95% CI = -1.95 to 7.63), whereas the other HRR cohort showed no early change in HRQoL from baseline (mean change = -0.07; 95% CI = -4.69 to 4.55) and declined by cycle 10 (mean change = -5.10; 95% CI = -15.3 to 5.06). Median time to deterioration in pain intensity and pain interference could not be estimated in either cohort. CONCLUSIONS: Patients with advanced mCRPC and BRCA alterations treated with niraparib experienced more meaningful improvement in overall HRQoL, pain intensity, and pain interference compared with those with other HRR alterations. In this population of castrate, heavily pretreated patients with mCRPC and HRR alterations, stabilization, and improvement in HRQoL may be relevant to consider when making treatment decisions. DISCLOSURES: This work was supported by Janssen Research & Development, LLC (no grant number). Dr Smith has received grants and personal fees from Bayer, Amgen, Janssen, and Lilly; and has received personal fees from Astellas Pharma, Novartis, and Pfizer. Dr Sandhu has received grants from Amgen, Endocyte, and Genentech; has received grants and personal fees from AstraZeneca and Merck; and has received personal fees from Bristol Myers Squibb and Merck Serono. Dr George has received personal fees from the American Association for Cancer Research, Axess Oncology, Capio Biosciences, Constellation Pharma, EMD Serono, Flatiron, Ipsen, Merck Sharp & Dohme, Michael J. Hennessey Association, Millennium Medical Publishing, Modra Pharma, Myovant Sciences, Inc., NCI Genitourinary, Nektar Therapeutics, Physician Education Resource, Propella TX, RevHealth, LLC, and UroGPO; has received grants and personal fees from Astellas Pharma, AstraZeneca, Bristol Myers Squibb, and Pfizer; has received personal fees and nonfinancial support from Bayer and UroToday; has received grants from Calithera and Novartis; and has received grants, personal fees, and nonfinancial support from Exelixis, Inc., Sanofi, and Janssen Pharma. Dr Chi has received grants from Janssen during the conduct of the study; has received grants and personal fees from AstraZeneca, Bayer, Astellas Pharma, Novartis, Pfizer, POINT Biopharma, Roche, and Sanofi; and has received personal fees from Daiichi Sankyo, Merck, and Bristol Myers Squibb. Dr Saad has received grants, personal fees, and nonfinancial support from Janssen during the conduct of the study; and has received grants, personal fees, and nonfinancial support from AstraZeneca, Astellas Pharma, Pfizer, Bayer, Myovant, Sanofi, and Novartis. Dr Thiery-Vuillemin has received grants, personal fees, and nonfinancial support from Pfizer; has received personal fees and nonfinancial support from AstraZeneca, Janssen, Ipsen, Roche/Genentech, Merck Sharp & Dohme, and Astellas Pharma; and has received personal fees from Sanofi, Novartis, and Bristol Myers Squibb. Dr Olmos has received grants, personal fees, and nonfinancial support from AstraZeneca, Bayer, Janssen, and Pfizer; has received personal fees from Clovis, Daiichi Sankyo, and Merck Sharp & Dohme; and has received nonfinancial support from Astellas Pharma, F. Hoffman-LaRoche, Genentech, and Ipsen. Dr Danila has received research support from the US Department of Defense, the American Society of Clinical Oncology, the Prostate Cancer Foundation, Stand Up to Cancer, Janssen Research & Development, Astellas Pharma, Medivation, Agensys, Genentech, and CreaTV. Dr Gafanov has received grants from Janssen during the conduct of the study. Dr Castro has received grants from Janssen during the conduct of the study; has received grants and personal fees from Janssen, Bayer, AstraZeneca, and Pfizer; and has received personal fees from Astellas Pharma, Merck Sharp & Dohme, Roche, and Clovis. Dr Moon has received research funding from SeaGen, HuyaBio, Janssen, BMS, Aveo, Xencor, and has received personal fees from Axess Oncology, MJH, EMD Serono, and Pfizer. Dr Joshua has received nonfinancial support from Janssen; consulted or served in an advisory role for Neoleukin, Janssen Oncology, Ipsen, AstraZeneca, Sanofi, Noxopharm, IQvia, Pfizer, Novartis, Bristol Myers Squibb, Merck Serono, and Eisai; and received research funding from Bristol Myers Squibb, Janssen Oncology, Merck Sharp & Dohme, Mayne Pharma, Roche/Genentech, Bayer, MacroGenics, Lilly, Pfizer, AstraZeneca, and Corvus Pharmaceuticals. Drs Mason, Liu, Bevans, Lopez-Gitlitz, and Francis and Mr Espina are employees of Janssen Research & Development. Dr Mason owns stocks with Janssen. Dr Fizazi has participated in advisory boards and talks for Amgen, Astellas, AstraZeneca, Bayer, Clovis, Daiichi Sankyo, Janssen, MSD, Novartis/AAA, Pfizer, and Sanofi, with honoraria to his institution (Institut Gustave Roussy); has participated in advisory boards for, with personal honoraria from, Arvinas, CureVac, MacroGenics, and Orion. Study registration number: NCT02854436.

Niraparib and Abiraterone Acetate for Metastatic Castration-Resistant Prostate Cancer

PURPOSE

Metastatic castration-resistant prostate cancer (mCRPC) remains a lethal disease with current standard-of-care therapies. Homologous recombination repair (HRR) gene alterations, including BRCA1/2 alterations, can sensitize cancer cells to poly (ADP-ribose) polymerase inhibition, which may improve outcomes in treatment-naïve mCRPC when combined with androgen receptor signaling inhibition.

METHODS

MAGNITUDE (ClinicalTrials.gov identifier: NCT03748641) is a phase III, randomized, double-blinded study that evaluates niraparib and abiraterone acetate plus prednisone (niraparib + AAP) in patients with (HRR+, n = 423) or without (HRR-, n = 247) HRR-associated gene alterations, as prospectively determined by tissue/plasma-based assays. Patients were assigned 1:1 to receive niraparib + AAP or placebo + AAP. The primary end point, radiographic progression-free survival (rPFS) assessed by central review, was evaluated first in the BRCA1/2 subgroup and then in the full HRR+ cohort, with secondary end points analyzed for the full HRR+ cohort if rPFS was statistically significant. A futility analysis was preplanned in the HRR- cohort.

RESULTS

Median rPFS in the BRCA1/2 subgroup was significantly longer in the niraparib + AAP group compared with the placebo + AAP group (16.6 v 10.9 months; hazard ratio [HR], 0.53; 95% CI, 0.36 to 0.79; P = .001). In the overall HRR+ cohort, rPFS was significantly longer in the niraparib + AAP group compared with the placebo + AAP group (16.5 v 13.7 months; HR, 0.73; 95% CI, 0.56 to 0.96; P = .022). These findings were supported by improvement in the secondary end points of time to symptomatic progression and time to initiation of cytotoxic chemotherapy. In the HRR- cohort, futility was declared per the prespecified criteria. Treatment with niraparib + AAP was tolerable, with anemia and hypertension as the most reported grade ≥ 3 adverse events.

CONCLUSION

Combination treatment with niraparib + AAP significantly lengthened rPFS in patients with HRR+ mCRPC compared with standard-of-care AAP.

[Media: see text].

Abstract 4133: High prevalence and heterogeneity of emergence of BRCA reversion mutations at progression on niraparib treatment in BRCA-mutant metastatic castration-resistant prostate cancer (mCRPC) patients

In the phase 2 GALAHAD study (NCT02854436), the PARP inhibitor (PARPi) niraparib, was evaluated in heavily pre-treated patients with mCRPC and DNA-repair gene defects (DRD) who progressed after androgen-receptor (AR) targeted therapy and taxane-based chemotherapy. The results showed that objective response rate (ORR) was 34.2% for patients with measurable disease having biallelic BRCA1/2 alterations (n=76). The development of BRCA reversion mutations, a type of secondary mutation that restores protein function, has been proposed as a key resistance mechanism to PARP inhibition. We aimed to evaluate the relationship between reversion mutations and treatment response in BRCA1/2 altered patients treated with niraparib in the GALAHAD study.

Thirty-three patients with biallelic BRCA alterations (excluding patients with homozygous deletions) had donated an end-of-treatment (EOT) ctDNA sample. We performed sequencing to detect reversion mutations using the Resolution Bioscience ctDx-HRD assay. Mutation patterns at baseline included splice site, nonsense, missense, and frameshift mutations, with the latter being the most common (24/33; 73%). No reversions were detected at baseline and the baseline BRCA alterations were detected at EOT for every patient. Most BRCA patients (28/33; 85%) had at least 1 reversion mutation (range: 1-38 different BRCA alterations) at EOT. Of the 28 patients with reversions, 5 were classified as low reversions: 3 patients had only one reversion mutation, 1 patient had 2 reversions at low allele frequency and 1 patient had 4 reversions at low allele frequency. Patients with reversion mutations showed better composite response (defined as ORR by RECIST 1.1, or CTC conversion to <5/7.5 mL blood, or ≥50% decline in prostate specific antigen) (74.2% vs 25.8%, p=0.01) and longer duration on treatment (median 6.9 vs 3.7 mo, p<0.05) compared to those without or low reversions. Additionally, patients with reversions trended to have longer median radiographic progression-free survival compared to those without or low reversions (8.1 vs 5.5 mo, p=0.12). In conclusion, the high prevalence of patients with BRCA reversion mutations and the displayed longer benefit from niraparib underscores the dependence of these tumors on BRCA mutation as an oncogenic driver and reversion mutations as a marker of secondary resistance to niraparib treatment.

Citation Format: Karen Urtishak, Gerhardt Attard, Tokuwa Kanno, Shibu Thomas, Gary E. Mason, Byron Espina, Eugene Zhu, Natalie Hutnick, Mary Guckert, Adam del Corral, Mark Li, Angela Lopez-Gitlitz, Kim Chi, William Kevin Kelly, Evan Y. Yu, Karim Fizazi, Matthew Smith. High prevalence and heterogeneity of emergence of BRCA reversion mutations at progression on niraparib treatment in BRCA-mutant metastatic castration-resistant prostate cancer (mCRPC) patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4133.

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]

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]

Efficacy and safety exposure-response relationships of apalutamide in patients with metastatic castration-sensitive prostate cancer: results from the phase 3 TITAN study

PURPOSE

Apalutamide plus androgen-deprivation therapy (ADT) has been approved for treatment of patients with metastatic castration-sensitive prostate cancer (mCSPC) based on data from phase 3 TITAN study. This analysis was conducted to describe pharmacokinetics of apalutamide and N-desmethyl-apalutamide and explore relationships between apalutamide exposure and selected clinical efficacy and safety observations.

METHODS

1052 patients were randomized to apalutamide + ADT (n = 525) or placebo + ADT (n = 527). A previously developed population pharmacokinetic model was applied. Cox regression analysis investigated the relationships between apalutamide exposure and overall survival (OS; n = 1004) and radiographic progression-free survival (rPFS; n = 1003). Logistic regression analysis assessed the relationships between apalutamide exposure and selected clinically relevant adverse events (n = 1051).

RESULTS

Apalutamide + ADT treatment was efficacious in extending rPFS and OS versus placebo + ADT. Within a relatively narrow apalutamide exposure range (coefficient of variation: 22%), no statistical association was detected between rPFS, OS and apalutamide exposure quartiles. Incidence of skin rash and pruritus increased significantly with increasing apalutamide exposure.

CONCLUSIONS

Differences in apalutamide exposure were not associated with clinically relevant differences in rPFS or OS in patients with mCSPC. Patients with increased apalutamide exposure are more likely to develop skin rash and pruritus. Dose reductions may improve these adverse events, based on an individual risk-benefit approach.

Deep Prostate-specific Antigen Response following Addition of Apalutamide to Ongoing Androgen Deprivation Therapy and Long-term Clinical Benefit in SPARTAN

BACKGROUND

Apalutamide plus androgen deprivation therapy (ADT) significantly improved metastasis-free survival (MFS), overall survival (OS), and time to prostate-specific antigen (PSA) progression in the placebo-controlled SPARTAN study of high-risk nonmetastatic castration-resistant prostate cancer (nmCRPC).

OBJECTIVE

To assess the relationships between PSA kinetics, outcomes, and molecular subtypes in SPARTAN.

DESIGN, SETTING, AND PARTICIPANTS

The authors conducted a post hoc analysis of nmCRPC patients randomized to receive apalutamide (n = 806) or placebo (n = 401) plus ADT and a subset stratified by molecular classifiers.

INTERVENTION

Apalutamide 240 mg/d.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The association between PSA kinetics and MFS, OS, time to PSA progression, and molecular subtypes was evaluated using the landmark analysis and Kaplan-Meier methods.

RESULTS AND LIMITATIONS

By 3 mo, PSA decreased in most apalutamide-treated patients and increased in most placebo-treated patients. After apalutamide, the median time to PSA nadir, confirmed ≥50% PSA reduction, ≥90% PSA reduction, and PSA ≤0.2 ng/ml were 7.4, 1.0, 1.9, and 2.8 mo, respectively. By 6 mo, 90%, 57%, and 32% of apalutamide patients had ≥50% PSA reduction, ≥90% PSA reduction, and PSA ≤0.2 ng/ml, respectively, while only 1.5% of placebo patients experienced ≥50% PSA reduction. PSA reductions were observed within 3 mo and up to 12 mo of apalutamide treatment, and were similar across molecular subtypes. Deep PSA responses (≥90% PSA reduction or PSA ≤0.2 ng/ml) at landmark 6-mo apalutamide treatment were significantly associated with improved time to PSA progression (hazard ratio {HR} [95% confidence interval {CI}] 0.25 [0.18-0.33] or 0.13 [0.08-0.21]), MFS (0.41 [0.29-0.57] or 0.3 [0.19-0.47]), and OS (0.45 [0.35-0.59] or 0.26 [0.18-0.38]; p < 0.001 for all).

CONCLUSIONS

Apalutamide plus ADT produced rapid, deep, and durable PSA responses by 6-mo treatment regardless of assessed molecular prognostic markers. An early PSA response with apalutamide was associated with clinical benefits, supporting prognostic value of PSA monitoring.

PATIENT SUMMARY

In this report, we describe how prostate-specific antigen (PSA) levels relate to outcomes in patients with nonmetastatic castration-resistant prostate cancer treated with apalutamide plus androgen deprivation therapy (ADT). We found that treatment with apalutamide plus ADT resulted in rapid, deep, and durable PSA responses in the majority of patients, including those with high-risk molecular subtypes, which were associated with improved survival.

Blood Biomarker Landscape in Patients with High-risk Nonmetastatic Castration-Resistant Prostate Cancer Treated with Apalutamide and Androgen-Deprivation Therapy as They Progress to Metastatic Disease

PURPOSE

In the placebo-controlled SPARTAN study, apalutamide added to androgen-deprivation therapy (ADT) improved metastasis-free survival, second progression-free survival (PFS2), and overall survival (OS) in patients with nonmetastatic castration-resistant prostate cancer (nmCRPC). Mechanisms of resistance to apalutamide in nmCRPC require evaluation.

PATIENTS AND METHODS

In a subset of patients from SPARTAN, aberrations were assessed at baseline and end of study treatment (EOST) using targeted next-generation sequencing or qRT-PCR. Circulating-tumor DNA (ctDNA) levels were assessed qualitatively. Select aberrations in androgen receptor (AR) and other common PC-driving genes were detected and summarized by the treatment group; genomic aberrations were summarized in ctDNA-positive samples. Association between detection of aberrations in all patients and outcomes was assessed using Cox proportional-hazards models and multivariate analysis.

RESULTS

In 247 patients, the overall prevalence of ctDNA, AR aberrations, and TP53 inactivation increased from baseline (40.6%, 13.6%, and 22.2%) to EOST (57.1%, 25.4%, and 35.0%) and was comparable between treatment groups at EOST. In patients who received subsequent androgen signaling inhibition after study treatment, detectable biomarkers at EOST were significantly associated with poor outcomes: ctDNA with PFS2 or OS (HR, 2.01 or 2.17, respectively; P < 0.0001 for both), any AR aberration with PFS2 (1.74; P = 0.024), and TP53 or BRCA2 inactivation with OS (2.06; P = 0.003; or 3.1; P < 0.0001).

CONCLUSIONS

Apalutamide plus ADT did not increase detectable AR/non-AR aberrations over ADT alone. Detectable ctDNA, AR aberrations, and TP53/BRCA2 inactivation at EOST were associated with poor outcomes in patients treated with first subsequent androgen signaling inhibitor.

AMPLITUDE: A study of niraparib in combination with abiraterone acetate plus prednisone (AAP) versus AAP for the treatment of patients with deleterious germline or somatic homologous recombination repair (HRR) gene-altered metastatic castration-sensitive prostate cancer (mCSPC)

TPS176

Background: Clinical benefit has been observed with poly(ADP-ribose) polymerase (PARP) inhibition in patients with metastatic castration-resistant prostate cancer tumors that carry HRR gene defects. Niraparib is a highly selective and potent PARP inhibitor, with activity against PARP-1 and PARP-2 deoxyribonucleic acid (DNA)-repair polymerases. The objective of AMPLITUDE is to assess the efficacy and safety of niraparib/placebo added to AAP with androgen deprivation therapy (ADT) in a biomarker-selected population with mCSPC. Methods: AMPLITUDE (NCT04497844) is a phase 3, randomized, double-blind, placebo-controlled study with an expected enrollment of 788 patients at ~350 sites in ~30 countries. Clinical trial information: NCT04497844. [Table: see text]

Apalutamide for metastatic, castration-sensitive prostate cancer in the Japanese population: A subgroup analysis of the randomized, double-blind, placebo-controlled phase 3 TITAN study

OBJECTIVE

To evaluate the efficacy and safety of apalutamide + androgen deprivation therapy versus androgen deprivation therapy alone in Japanese patients with metastatic castration-sensitive prostate cancer from the phase 3, randomized, global TITAN study.

METHODS

Men with metastatic castration-sensitive prostate cancer randomly (1:1) received 240 mg apalutamide + androgen deprivation therapy or matching placebo + androgen deprivation therapy. The primary efficacy endpoints were radiographic progression-free survival and overall survival. Secondary efficacy endpoints were time to cytotoxic chemotherapy, pain progression, chronic opioid use, and skeletal-related events. Safety was also assessed.

RESULTS

Of the 1052 patients included in the TITAN study, 51 (4.85%) were Japanese (apalutamide group, n = 28; placebo group, n = 23). In all, 81.8% of patients in the apalutamide and 71.8% in the placebo group did not experience radiographic progression or death, and the hazard ratio for radiographic progression-free survival favored treatment with apalutamide (hazard ratio 0.712, 95% confidence interval 0.205-2.466; P = 0.59). At 24 months, 85.7% of patients in the apalutamide group and 81.5% in the placebo group were alive, and the hazard ratio for overall survival favored apalutamide (hazard ratio 0.840, 95% confidence interval 0.210-3.361; P = 0.805). In the interim analysis, the median radiographic progression-free survival and overall survival were not reached in the apalutamide group and time to cytotoxic chemotherapy was delayed following apalutamide treatment. The safety profile of apalutamide in the Japanese subpopulation was comparable with that of the global population, except for skin rash.

CONCLUSIONS

The results of the present analyses suggest that apalutamide + androgen deprivation therapy in Japanese patients had favorable efficacy compared with androgen deprivation therapy alone, and these findings are comparable to those in the overall population. Apalutamide + androgen deprivation therapy can be considered as one of the therapeutic options for a broad spectrum of metastatic castration-sensitive prostate cancer regardless of prior treatment and disease extent in Japanese patients.

Apalutamide and Overall Survival in Prostate Cancer

BACKGROUND

The phase 3 SPARTAN study evaluated apalutamide versus placebo in patients with nonmetastatic castration-resistant prostate cancer (nmCRPC) and prostate-specific antigen doubling time of ≤10 mo. At primary analysis, apalutamide improved median metastasis-free survival (MFS) by 2 yr and overall survival (OS) data were immature.

OBJECTIVE

We report the prespecified event-driven final analysis for OS.

DESIGN, SETTING, AND PARTICIPANTS

A total of 1207 patients with nmCRPC (diagnosed by conventional imaging) were randomised 2:1 to apalutamide (240mg/d) or placebo, plus on-going androgen deprivation therapy. After MFS was met and the study was unblinded, 76 (19%) patients still receiving placebo crossed over to apalutamide.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

OS and time to cytotoxic chemotherapy (TTChemo) were analysed by group-sequential testing with O'Brien-Fleming-type alpha spending function.

RESULTS AND LIMITATIONS

At median 52-mo follow-up, 428 deaths had occurred. The median treatment duration was 32.9 mo for apalutamide group and 11.5 mo for placebo group. Median OS was markedly longer with apalutamide versus placebo, reaching prespecified statistical significance (73.9 vs 59.9 mo, hazard ratio [HR]: 0.78 [95% confidence interval {CI}, 0.64-0.96]; p=0.016). Apalutamide also lengthened TTChemo versus placebo (HR: 0.63 [95% CI, 0.49-0.81]; p=0.0002). Discontinuation rates in apalutamide and placebo groups due to progressive disease were 43% and 74%, and due to adverse events 15% and 8.4%, respectively. Subsequent life-prolonging therapy was received by 371 (46%) patients in the apalutamide arm and by 338 (84%) patients in the placebo arm including 59 patients who received apalutamide after crossover. Safety was consistent with previous reports; when adverse events were adjusted for treatment exposure, rash had the greatest difference of incidence between the apalutamide and placebo groups.

CONCLUSIONS

Extension of OS with apalutamide compared with placebo conferred impactful benefit in patients with nmCRPC. There was a 22% reduction in the hazard of death in the apalutamide group despite 19% crossover (placebo to apalutamide) and higher rates of subsequent therapy in the placebo group.

PATIENT SUMMARY

With data presented herein, all primary and secondary study end points of SPARTAN were met; findings demonstrate the value of apalutamide as a treatment option for nonmetastatic castration-resistant prostate cancer.

Skin rash following Administration of Apalutamide in Japanese patients with Advanced Prostate Cancer: an integrated analysis of the phase 3 SPARTAN and TITAN studies and a phase 1 open-label study

BACKGROUND

A higher incidence of apalutamide-related skin rash has been observed in Japanese patients with prostate cancer (PC).

METHODS

This integrated analysis of data of Japanese patients from 2 global Phase 3 studies, SPARTAN ( NCT01946204 ; patients with non-metastatic castration-resistant PC [nmCRPC]) and TITAN ( NCT02489318 ; patients with metastatic castration-sensitive PC [mCSPC]), and the Phase 1 study 56021927PCR1008 ( NCT02162836 ; patients with metastatic CRPC [mCRPC]), assessed clinical risk factors of apalutamide-related skin rash as well as the potential correlation with plasma exposure to apalutamide. Kaplan-Meier method was used for time-to-event analyses. Clinical risk factors for skin rash were assessed using odds ratio.

RESULTS

Data from 68 patients (SPARTAN: n = 34, TITAN: n = 28, 56021927PCR1008: n = 6) receiving apalutamide 240 mg orally once-daily were analyzed. Rash (13 [19.1%]) and maculo-papular rash (11 [16.2%]) were the most frequently reported skin rash. All Grade and Grade 3 skin rash occurred in 35 (51.5%) and 10 (14.7%) patients, respectively. Most (85.7%) skin rash occurred within 4 months of apalutamide initiation and resolved in a median time of 1 month following the use of antihistamines, topical or systemic corticosteroids, with/without apalutamide dose interruptions/reductions. Median time-to-remission of first incidence of rash and maximum grade incidence of rash were 1.0 month (IQR: 0.36-1.81) and 1.0 month (IQR: 0.30-2.43), respectively. No significant clinical risk factors for the incidence of skin rash were observed. Areas under the curve (0-24 h) (AUC0-24, ss) at steady-state of plasma apalutamide concentration were numerically slightly higher in patients with skin rash than those without.

CONCLUSIONS

No clinical risk factors for rash could be detected. There is a potential correlation between incidence of skin rash and plasma exposure to apalutamide. In general, apalutamide-related skin rash is easily managed, with appropriate treatment with or without dose adjustment.

TRIAL REGISTRATION

Retrospective pooled analysis of NCT01946204 , NCT02489318 , and NCT02162836 .

Abstract 776: Androgen receptor (AR) and non-AR aberrations associated with outcomes in metastatic castration-sensitive prostate cancer (mCSPC) treated with apalutamide (APA) plus androgen deprivation therapy (ADT) in TITAN

Background: In TITAN, APA improved radiographic progression-free survival (rPFS), overall survival (OS), and second progression-free survival (PFS2) vs placebo (PBO) in patients (pts) with mCSPC receiving ADT. We determined the presence of genomic and transcriptional aberrations and evaluated associations of these aberrations with clinical outcomes in TITAN.

Methods: Whole-blood samples from 130 pts were collected at baseline (BL, n = 59) and end of treatment (EOT: APA, n = 47; PBO, n = 83). Circulating tumor (ct)DNA and non-AR aberrations (Table) were assessed from isolated cell-free (cf)DNA (n = 129), and AR aberrations at EOT were assessed from cfDNA and cellular RNA (n = 127) using next-generation sequencing and real-time PCR. Detected biomarkers at BL and EOT were assessed for associations with rPFS, OS, and PFS2 and with OS and PFS2, respectively, using Cox proportional hazards model and multivariate analyses (MVA) in pooled APA and PBO pts.

Table.Frequency of aberrations and univariate analyses of the association between aberration status at EOT with outcomesAberrationsBL, n (%)EOT, n (%)HR (95% CI) p value for shorter outcomes by aberration-positive vs -negative status (reference)APAPBOOverallAPAPBOOverallPFS2OSn = 15n = 44n = 59n = 47n = 82n = 129ctDNA6 (40)19 (43)25 (42)32 (68)66 (80)98 (76)3.55 (1.59-7.92)7.77 (2.40-25.13)p = 0.002p = 0.001Any AR aberrationa3 (20)10 (23)13 (22)n = 46n = 81n = 1272.82 (1.58-5.03)3.70 (1.85-7.41)22 (48)54 (67)76 (59)p = 0.0002p = 0.0001TP53 inactivationb1 (7)7 (16)8 (14)14 (30)36 (44)50(39)2.42 (1.45-4.04)2.69 (1.54-4.71)p = 0.001p = 0.001RB1 inactivationb2 (13)2 (5)4 (7)13 (28)19 (23)32 (25)1.86 (1.08-3.21)2.08 (1.18-3.66)p = 0.026p = 0.011PIK3CA amplification/SNV2 (13)2 (5)4 (7)13 (28)16 (20)29 (22)2.30 (1.34-3.94)3.06 (1.75-5.36)p = 0.002p &lt; 0.001MYC amplification/SNV1 (7)3 (7)4 (7)6 (13)7 (9)13 (10)1.64 (0.77-3.48)2.35 (1.10-5.02)p = 0.198p = 0.027CDK12 inactivationb01 (2)1 (2)1 (2)5 (6)6 (5)1.54 (0.56-4.28)2.55 (1.00-6.47)p = 0.406p = 0.050MET amplification/SNV0001 (2)9 (11)10 (8)1.59 (0.72-3.52)2.90 (1.28-6.56)p=0.253p=0.010aDefined as AR ligand-binding domain mutations (L702H, W742C, H875Y, F877L, and T878A), or AR copy number gain, or ARv7 transcript detection.bDefined as either heterozygous or homozygous deletion or single nucleotide variant (SNV) with known pathogenic consequence based on ClinVar, an archive of human variations and phenotypes.

Results: From BL to EOT, detection of ctDNA increased 1.8-fold and similarly with APA and PBO; detection of AR aberrations increased 2.7-fold and was less frequent with APA vs PBO (Table; p = 0.04, Fisher exact test). Among non-AR aberrations at EOT, those in TP53, RB1, PI3KCA were the most frequent; detection increased ≥ 2.8-fold from BL to EOT and similarly with APA and PBO (Table). Detection of ctDNA, AR aberrations, and aberrations in TP53, RB1, PI3KCA at EOT were associated with shorter PFS2 and OS (Table). Detection of other non-AR aberrations at EOT and of all aberrations at BL was low for robust conclusions. Only detectable ctDNA at EOT maintained association with shorter OS in MVA.

Conclusions: In TITAN pts with mCSPC, AR and several non-AR aberrations were most frequent at progression. APA was associated with decreased frequency of AR aberrations at EOT and similar frequency of detectable ctDNA vs PBO. ctDNA was an independent prognostic variable for shorter PFS2 and OS in pts with mCSPC.

Citation Format: Kim N. Chi, Shibu Thomas, Michael Gormley, Dong Shen, Neeraj Agarwal, Felix Feng, Gerhardt Attard, Alex Wyatt, Deborah S. Ricci, Angela Lopez-Gitlitz, Julie S. Larsen, Branko Miladinovic, Simon Chowdhury. Androgen receptor (AR) and non-AR aberrations associated with outcomes in metastatic castration-sensitive prostate cancer (mCSPC) treated with apalutamide (APA) plus androgen deprivation therapy (ADT) in TITAN [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 776.

Abstract 5425: Novel molecular subtypes identified in prostate cancer: Results from the SPARTAN study

Background: Results from SPARTAN, a phase III placebo (PBO)-controlled study in patients (pts) with nonmetastatic castration-resistant prostate cancer (nmCRPC), show that apalutamide (APA) plus ongoing androgen deprivation therapy (ADT) significantly improves metastasis-free survival (MFS) compared with PBO + ADT. This analysis investigated the effects of APA in biologically distinct molecular subclasses of prostate cancer defined by gene expression profiles.

Methods: Gene expression profiles (DECIPHER® prostate test, San Diego, CA) were generated from 233 archival primary prostate tumors; data were summarized based on 160 predefined gene signatures indicative of clinical prognosis and prostate cancer-related biology. Unsupervised consensus clustering identified sets of co-regulated expression signatures, and associations between signature expression, treatment, and signature-treatment interaction with MFS were evaluated using Kaplan-Meier analysis and Cox proportional hazards models.

Results: Four co-regulated expression signature classes, each with distinct biological pathway functions, were identified. Class C1 included prognosis-related (risk) signatures; C2 included steroid homeostasis-related signatures; C3 included hormonal therapy nonresponsive basal and neuroendocrine-like signatures; C4 included immune and stromal signatures. Increased C1 expression was associated with shorter MFS in the PBO group (HR [95% CI], 2.18 [1.11-4.28], p = 0.02), while it was associated with longer MFS in the APA group (interaction HR [95% CI], APA vs PBO, 0.36 [0.14-0.95], p = 0.04). Similarly, increased C2 expression was associated with shorter MFS in the PBO group (HR [95% CI], 1.42 [1.02-1.98], p = 0.04), while it was associated with longer MFS in the APA group (interaction HR [95% CI], APA vs PBO, 0.57 [0.35-0.93], p = 0.02). Although there is no significant interaction effect between signature and treatment in C3, pts with low expression of C3 (adeno-like) showed longer MFS on APA vs PBO (HR [95% CI], 0.23 [0.13-0.40], p &lt; 0.0001) compared with high-C3-expressing neuroendocrine-like tumors. Increased C4 expression was associated with decreased risk of metastasis in the APA group (HR [95% CI], 0.55 [0.35-0.86], p = 0.008) compared with PBO (interaction HR [95% CI], APA vs PBO, 0.53 [0.28-0.98], p = 0.04).

Conclusion: Expression signatures were clustered into 4 correlated unique biological subclasses. Clinical benefit of APA + ADT was observed in pts with expression profiles with high risk (C1), C2, C3, or C4 compared with PBO + ADT.

Citation Format: Clemente Aguilar, Michael Gormley, Shibu Thomas, Paul N. Mainwaring, David Olmos, Fred Saad, Simon Chowdhury, Elai Davicioni, Yang Liu, Deborah S. Ricci, Angela Lopez-Gitlitz, Margaret K. Yu, Matthew R. Smith, Eric J. Small, Felix Feng. Novel molecular subtypes identified in prostate cancer: Results from the SPARTAN study [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5425.

Molecular determinants of outcome for metastatic castration-sensitive prostate cancer (mCSPC) with addition of apalutamide (APA) or placebo (PBO) to androgen deprivation therapy (ADT) in TITAN

5535

Background: In TITAN, addition of APA to ADT improved radiographic progression-free survival (rPFS) and overall survival (OS) versus PBO plus ADT in patients (pts) with mCSPC. In this post hoc analysis, we performed transcriptome-wide profiling of tumor samples and assessed association of molecular subtypes with rPFS. Methods: The DECIPHER platform (Decipher Biosciences, Inc.) was used to assess gene expression in archival primary prostate tumors from TITAN. Samples were classified into high versus low to average risk of metastases (DECIPHER genomic classifier [GC] > 0.6 and ≤ 0.6, respectively), basal and luminal A/B (PAM50 classifier), and androgen receptor activity (AR-A) signature high and low. Associations between subtypes with rPFS were assessed with Cox proportional hazards model. Results: The biomarker population included 222 pts (APA, 110; PBO, 112). Benefit in rPFS from APA in the biomarker population (HR [95% CI]; p value; 0.49 [0.31-0.78]; 0.002) resembled that in the overall study population (0.49 [0.40-0.61]; < 0.0001). The majority of TITAN pts had GC high scores (n = 166, 75%). GC high risk subtype in the PBO group had poorer prognosis for rPFS than GC low to average risk subtype (median rPFS 18.2 mos for GC high vs not reached [NR] for GC low to average, 0.28 [0.11-0.69]; 0.006), but there was no difference in prognosis between high and low to average GC risk subtypes in the APA group (GC high NR vs GC low to average NR; 0.81 [0.35-1.89]; 0.625). Pts were further stratified based on basal/luminal and AR-A signatures. Basal (n = 112, 50%) and AR-A low (n = 96, 43%) subtypes, known to be nonresponsive to ADT, both showed significant benefit from APA vs PBO (0.30 [0.16-0.57]; < 0.001 and 0.25 [0.12-0.52]; < 0.001, respectively). The majority of AR-A low subtype (74%, 71/96) overlapped with basal subtype. Further conclusions for risk of rPFS in GC low, luminal, and AR-A high subtypes and OS across all subtypes will be assessed as more events occur. Conclusions: In TITAN, addition of APA to ADT improved rPFS for all subtypes of pts with mCSPC. APA overcame the poor prognosis of GC high risk subtype and prolonged rPFS in ADT-resistant AR-A low and basal molecular subtypes, suggesting APA is beneficial especially for the highest risk molecular subtypes. Clinical trial information: NCT02489318 .

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]

Computational pathological identification of prostate cancer following neoadjuvant treatment

e14052

Background: The need for accurate pathological identification and quantitation of prostate cancer (PC) following neoadjuvant treatment with androgen deprivation therapy (ADT) and androgen receptor antagonists is increasing as PC treatment continues to evolve. In clinical practice, pathological assessment of residual tumor is a tedious and time-consuming process due to the volume of tissue from radical prostatectomy (RP). In addition, neoadjuvant treatments can greatly alter both benign and neoplastic prostate tissue morphology making the pathology assessment difficult for even specialized pathologists. Paige Prostate 1.0 is a clinical-grade artificial intelligence (AI) system for PC detection. It was trained and evaluated in over 50,000 prostate biopsy slides with validation across more than 800 institutions worldwide using multiple slide scanners. Methods: We evaluated the performance of Paige Prostate 1.0 at identifying prostatic tumor on 64 hematoxylin and eosin stained slides exhibiting neoadjuvant treatment effect from apalutamide, enzalutamide, and/or ADT. Results: Analysis of the receiver operating characteristic curve demonstrated an area under the curve of 0.96. Using the Paige Prostate 1.0 operating point, it achieved a sensitivity of 91% and a specificity of 94%, corresponding to the correct identification of challenging treated morphology in 59/64 slides using expert pathologists as the reference. False negative cases were typically represented by atypical small acinar proliferation that required expert pathological consensus confirmation. Conclusions: To our knowledge, this is the first AI based evaluation of residual disease in PC with hormone neoadjuvant therapy. Paige Prostate 1.0 effectively identified tumor despite treatment effects. Future work will include optimization of Paige Prostate 1.0 by training with RP specimens from a larger cohort of appropriate samples, as well as precise measurement of residual tumor burden to further improve its accuracy and reproducibility. Paige prostate residual disease detection 1.0 has the potential to impact emerging clinical practice at the patient level and to complement the pathological assessment of RPs in global phase 3 clinical trials, such as PROTEUS, in a standardized, reproducible, and robust way.

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]

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]

PROTEUS: A randomized, double-blind, placebo (PBO)-controlled, phase III trial of apalutamide (APA) plus androgen deprivation therapy (ADT) versus PBO plus ADT prior to radical prostatectomy (RP) in patients with localized high-risk or locally advanced prostate cancer (PC)

TPS383

Background: Patients (pts) with localized high-risk PC have disease progression rates of ~50% after RP (Kane et al. J Urol. 2007). Neoadjuvant studies show that androgen blockade can improve local disease control at the time of RP (McKay et al. Prostate Cancer Prostatic Dis. 2017; Taplin et al. JCO. 2014; Efstathiou et al. Eur Urol. 2019). This study will determine if treatment with APA + ADT before RP in pts with localized high-risk or locally advanced PC improves pathologic complete response (pCR) rate and if neoadjuvant and adjuvant peri-operative treatment with APA + ADT improves metastasis-free survival (MFS) compared with PBO + ADT. Methods: This international multicenter trial is enrolling candidates for RP with localized high-risk or locally advanced PC. Eligibility criteria: any combination of Gleason score (GS) 4 + 3 (= Grade Group [GG] 3) and GS 8 (4 + 4 or 5 + 3) from ≥ 6 systematic biopsy cores (SB) or targeted biopsy cores (TB) (with ≥ 1 core GS 8 [4 + 4 or 5 + 3] included); any combination of GS 4 + 3 (= GG 3) and GS 8 (4 + 4 or 5 + 3) from ≥ 3 SB or TB (with ≥ 1 core GS 8 [4 + 4 or 5 + 3]) included and prostate-specific antigen (PSA) ≥ 20 ng/mL; GS ≥ 9 (GG 5) in ≥ 1 SB or TB; or ≥ 2 SB or TB with continuous GS ≥ 8 (GG 4), each with ≥ 80% involvement. Stratification: GS (7 or ≥ 8), cN0 or N1, and region. Randomization: 1:1 to APA (240 mg) + ADT or PBO + ADT. Pts will receive 6 months neoadjuvant treatment and RP + 6 months adjuvant treatment. Dual primary end points: pCR rate (assessed by blinded independent central pathology review) and MFS (assessed by blinded independent central radiology review). Secondary end points: PSA-free survival and progression-free survival. Imaging with CT or MRI and bone scan at screening, after RP, and then every 6 months following biochemical failure until documented distant metastasis, or death. ~1500 pts will be enrolled globally over 3 years at 240 sites in 19 countries. An independent data monitoring committee is commissioned to review trial data. Clinical trial information: NCT03767244.

Apalutamide (APA) for metastatic castration-sensitive prostate cancer (mCSPC) in TITAN: Outcomes in patients (pts) with low- and high-risk disease

87

Background: TITAN showed that APA + androgen deprivation therapy (ADT) improves radiographic progression-free survival (rPFS) and overall survival (OS) in a broad group of pts with mCSPC (Chi et al. NEJM 2019). This post hoc analysis evaluates APA + ADT based on baseline (BL) prognostic risk as defined in LATITUDE (Fizazi et al. Lancet Oncol 2019). Methods: 1052 pts with mCSPC receiving ADT were randomized 1:1 to APA (240 mg/d; n = 525) or placebo (PBO; n = 527). Treatment cycles were 28 days. Risk included Gleason score ≥ 8, ≥ 3 bone lesions, or visceral metastasis. High risk was ≥ 2 risk factors, low risk was ≤ 1. Cox proportional hazards model was used to estimate HR and 95% CI for rPFS and OS. Results: Pt demographic and BL disease characteristics were similar between treatment groups (high risk: APA n = 289, PBO n = 286; low risk: APA n = 236, PBO n = 241). Median treatment duration was similar in the low-risk group with APA or PBO (21.8 mo and 20.3 mo, respectively). For the high-risk groups, treatment duration was longer with APA (APA 19.5 mo, PBO 14.7 mo). APA significantly reduced the risk of radiographic progression relative to PBO in both groups (Table). Risk of death (OS) was reduced by 38% in high-risk pts and 26% in low-risk pts with APA (Table). 24-mo survival rates: high risk, 76% APA, 63% PBO; low risk, 90% APA, 85% PBO. There were few deaths (≤ 33) in low-risk groups. Second PFS in APA pts: high risk, HR 1.9 (95% CI 1.2-3.0), p = 0.004; low risk, HR 2.2 (95% CI 1.5-3.2), p < 0.0001. Regardless of risk category, the safety profile of APA remained consistent with previously reported overall results. Conclusions: Addition of APA to ADT for pts with mCSPC prolonged rPFS and OS with a consistent safety profile compared with PBO + ADT regardless of BL risk. Clinical trial information: NCT02489318. [Table: see text]

A randomized phase II study of apalutamide (APA), androgen deprivation therapy (ADT), or APA + ADT in patients (pts) with biochemically relapsed (BCR) prostate cancer (PC)

320

Background: While there is no standard therapy for BCR PC following local therapy, intermittent ADT is widely used. We evaluated utility of APA alone, ADT (luteinizing hormone–releasing hormone agonist [LHRHa]) alone, or APA + LHRHa in ADT-naïve BCR PC pts. Methods: Pts with BCR PC after primary definitive local therapy and prostate-specific antigen (PSA) doubling time (PSADT) ≤ 12 mo were randomized 1:1:1 to open-label 240 mg APA daily, LHRHa alone, or APA + LHRHa for 12 mo, followed by a 12-mo observation period off therapy. Pts were stratified by PSADT (< 6 vs 6-12 mo) and age (≤ 70 vs > 70 y). Primary end point: mean change from baseline (BL) in health-related quality of life (HRQoL) per Functional Assessment of Cancer Therapy-Prostate total score at 12 mo. Secondary end points included PSA nadir < 0.2 ng/mL by 7 mo, time to PSA progression (TTPpsa), and time to testosterone (T) recovery. Results: 90 pts (APA, n = 29; LHRHa, n = 30; APA + LHRHa, n = 31) were treated for median of 12 mo with similar distribution of BL characteristics across groups: 67% age ≤ 70 y; 67% PSADT < 6 mo. There was no significant difference in HRQoL in APA vs LHRHa at 12 mo, or between LHRHa vs APA + LHRHa groups. At median follow-up of 30-33 mo, TTPpsa in APA, LHRHa, and APA + LHRHa groups was 26 mo, 31 mo, and 36 mo, respectively. Compared to LHRHa alone, APA + LHRHa resulted in a trend toward improved TTPpsa (HR [95% CI] 0.56 [0.23-1.36], p = 0.196), and APA alone resulted in a trend for shorter TTPpsa (HR 1.09 [0.49-2.43], p = 0.824). PSA nadir < 0.2 ng/mL was reached in 89%, 89%, and 97% in APA, LHRHa, and APA + LHRHa pts. Median time to T recovery was similar in LHRHa and APA + LHRHa groups (23 mo vs 24 mo). Grade 3-4 adverse events (AEs) occurred in 17% of APA, 14% of LHRHa, and 29% of APA + LHRHa pts. The only grade 3-4 AE reported in > 1 pt per group was hypertension (APA, 3%; LHRHa, 0; APA + LHRHa, 13%). Conclusions: Addition of APA to LHRHa resulted in a trend for longer TTPpsa and a higher proportion of pts achieving optimal PSA nadir without significant difference in HRQoL or time to T recovery. Observed AEs were consistent with known safety profiles. Results support further evaluation of APA + LHRHa for a specified duration in BCR PC. Clinical trial information: NCT01790126.

Time to second progression (PFS2) in patients (pts) from TITAN with metastatic castration-sensitive prostate cancer (mCSPC) by first subsequent therapy (hormonal vs. taxane)

82

Background: TITAN, a phase 3, randomized, double-blind study of apalutamide (APA) vs placebo (PBO) added to androgen deprivation therapy (ADT), demonstrated significant improvement in radiographic progression-free survival and overall survival in a broad pt population with mCSPC who received APA (Chi KN et al. NEJM 2019). This post hoc analysis evaluates whether type of 1st life-prolonging subsequent therapy (hormonal vs taxane) has an effect on PFS2 benefit shown with APA + ADT. Methods: PFS2 (the time from randomization to disease progression on 1st subsequent therapy for prostate cancer or death, whichever occurs first) was evaluated for pts from TITAN based on 1st subsequent life-prolonging therapy (hormonal vs taxane) after study treatment. Analysis censored all other 1st subsequent systemic therapies after start of treatment. Results: 277 pts (APA, 87; PBO, 190) received subsequent systemic therapy for prostate cancer; 86 pts (APA, 24; PBO, 62) received hormonal therapy (abiraterone acetate + prednisone or enzalutamide) and 99 (APA, 30; PBO, 69) received taxane (docetaxel or cabazitaxel) as 1st subsequent therapy. Baseline demographic and disease characteristics were generally similar between groups. The taxane group had a higher proportion of pts with high volume and pts with > 10 bone metastases, and a lower proportion with prior docetaxel exposure when compared with the hormonal group. Median treatment duration with APA and PBO was 11.9 and 11.1 mos in the hormonal group and 11.0 and 11.3 mos in the taxane group. Regardless of subsequent therapy, PFS2 was significantly longer for APA vs PBO (HR 0.66 [95% CI 0.50-0.87], p = 0.0026). Pts in both groups who received APA had a significant reduction in risk of 2nd progression compared with PBO (hormonal: HR 0.68 [0.48-0.97], p = 0.0326; taxane: HR 0.67 [0.48-0.94], p = 0.0189; medians not reached). Safety analyses were not conducted; all pts had discontinued therapy, most due to disease progression. Conclusions: The addition of APA to ADT for treatment of mCSPC results in risk reduction of 2nd progression regardless of choice of hormonal or taxane as the 1st life-prolonging subsequent therapy. Clinical trial information: NCT02489318.

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.

Understanding symptomatic experience, impact, and emotional response in recently diagnosed metastatic castration-resistant prostate cancer: a qualitative study

PURPOSE

We sought to explore the symptomatic experience of men recently told their castration-resistant prostate cancer has metastasized (mCRPC); the impact and emotional response to this; the emotional burden of monitoring development to metastatic status; and the emotional impact on the primary support person (PSP).

METHODS

Interviews were conducted with 25 men recently diagnosed with mCRPC from the United States (US), France, and Germany. We also interviewed 14 PSPs. Thematic analysis was conducted using Atlas.ti.

RESULTS

The mean age of patients was 72.2 years; mean time since metastasis 7.8 months. The most frequent symptoms were fatigue/tiredness, sexual dysfunction, and pain. Metastasis had a negative emotional impact on the patient and PSP. Some explicitly associated certain symptoms/impacts with metastasis, such as localized pain, diarrhea, blood in stool, and increased impact on activities of daily living. About 72% of patients highlighted the emotional impact of a metastatic diagnosis, reporting worry/anxiety/fear, low mood/depression, shock, increased burden on PSP, and strain on relationships. Monitoring prostate-specific antigen (PSA) values was important; ten patients explicitly discussed feeling fear/worry when PSA was rising, and glad/happy/excited when PSA was falling. Most reported that, if a medication had been available to them to delay metastasis, they would have taken it, even if they were asymptomatic.

CONCLUSIONS

Interviews highlighted the substantial burden of mCRPC to both patient and PSP. Development of metastasis was associated with symptoms worsening rather than the development of new symptoms, with physical and emotional impacts. Most patients were willing to take a medication to delay metastasis.

Prostate-Specific Membrane Antigen Ligand Positron Emission Tomography in Men with Nonmetastatic Castration-Resistant Prostate Cancer

PURPOSE

Systemic androgen-signaling inhibition added to ongoing androgen-deprivation therapy (ADT) improved clinical outcomes in patients with nonmetastatic castration-resistant prostate cancer without detectable metastases by conventional imaging (nmCRPC). Prostate-specific membrane antigen ligand positron emission tomography (PSMA-PET) detects prostate cancer with superior sensitivity to conventional imaging, but its performance in nmCRPC remains largely unknown. We characterized cancer burden in high-risk patients with nmCRPC using PSMA-PET.

EXPERIMENTAL DESIGN

We retrospectively included 200 patients with nmCRPC, prostate-specific antigen (PSA) >2 ng/mL, and high risk for metastatic disease [PSA doubling time (PSADT) of ≤10 months and/or Gleason score of ≥8] from six high-volume PET centers. We centrally reviewed PSMA-PET detection rate for pelvic disease and distant metastases (M1). We further evaluated SPARTAN patients stratified by risk factors for PSMA-PET-detected M1 disease.

RESULTS

PSMA-PET was positive in 196 of 200 patients. Overall, 44% had pelvic diseases, including 24% with local prostate bed recurrence, and 55% had M1 disease despite negative conventional imaging. Interobserver agreement was very high (κ: 0.81-0.91). PSA ≥ 5.5 ng/mL, locoregional nodal involvement determined by pathology (pN1), prior primary radiation, and prior salvage radiotherapy independently predicted M1 disease (all P < 0.05).

CONCLUSIONS

PSMA-PET detected any disease in nearly all patients and M1 disease in 55% of patients previously diagnosed with nmCRPC, including subgroups with PSADT of ≤10 months and Gleason score of ≥8. The value of PSMA-PET imaging for treatment guidance should be tested in future studies.

Abstract 1335: Digital droplet PCR (ddPCR)-based detection of androgen receptor splice variant 7 (AR-v7) in non-metastatic castration resistant prostate cancer

Background: The androgen receptor (AR) is a clinically important driver in prostate cancer. In metastatic castration resistant prostate cancer (mCRPC), increased expression of the ligand-independent AR variant 7 (AR-v7) is a biomarker of hormonal therapy resistance. However, the prevalence and clinical importance of AR-v7 in non-metastatic CRPC (nmCRPC) is not yet known. Low circulating tumor cell (CTC) frequencies in these patients make emergence of AR-v7 during anti-androgen therapy difficult to study. We report blood-based detection of AR-v7 using digital droplet PCR (ddPCR) in nmCRPC patients enrolled in the SPARTAN trial, a randomized phase 3 study testing ADT vs apalutamide (APA)+ADT.

Method: To investigate simultaneous and quantitative expression of AR-v7 and AR, we utilized ddPCR to measure individual mRNA transcripts in blood samples collected in PAXgene tubes. AR-v7 positivity was calculated as the normalized fraction of AR-v7 vs total AR transcripts (AR-v7/AR). Normalized AR-v7/AR frequency in healthy volunteers (HV) and mCRPC was measured to determine an expression cutoff to separate normal and prostate cancer blood samples. The ddPCR AR-v7 biomarker assay was then used to measure AR-v7 expression in ADT (N=47) and APA+ADT (N=53) SPARTAN samples taken at time of study initiation and correlated with clinical outcome.

Results: By setting a cutoff at 0.3 AR-v7/AR normalized fraction we could differentiate HV from mCRPC patients. In nmCRPC, mean AR-v7 and AR-FL expression were calculated as 1.2 and 349.3 transcripts, respectively. The 0.3 AR-v7/AR normalized fraction cutoff could not differentiate AR-v7 expression between HV and nmCRPC. Using this assay, we detected AR-v7 transcripts in 47% of nmCRPC SPARTAN patients analyzed. However, results of AR-v7 expression as a continuous and discretized variable were inconclusive when correlated with clinical outcome.

Conclusion: This study reports ddPCR-based detection of whole blood mRNA as a sensitive assay to detect simultaneously low and high expressing AR transcripts in nmCRPC. Our technical analysis demonstrates that unlike in mCRPC, low level transcript counts of AR-v7 in nmCRPC may not distinguish expression from baseline in healthy patients. Data from this limited cohort suggest that while AR-v7 is detected in 47% of patients, a higher threshold of expression may be biologically important for driving treatment resistance. Further analysis of this assay in mCRPC and APA refractory samples sequenced with other therapies are needed to confirm the clinical and biological utility of AR-v7 detection by ddPCR assay and inform disease continuum management.

Citation Format: Mel Pilar Espaillat, Yashoda Rajpurohit, Mike Gormley, Denis Smirnov, Ian McCaffery, Angela Lopez-Gitlitz, Deborah Ricci, Shibu Thomas. Digital droplet PCR (ddPCR)-based detection of androgen receptor splice variant 7 (AR-v7) in non-metastatic castration resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1335.

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)

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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)

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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

5024

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

42

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]

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.

Apalutamide Treatment and Metastasis-free Survival in Prostate Cancer

BACKGROUND

Apalutamide, a competitive inhibitor of the androgen receptor, is under development for the treatment of prostate cancer. We evaluated the efficacy of apalutamide in men with nonmetastatic castration-resistant prostate cancer who were at high risk for the development of metastasis.

METHODS

We conducted a double-blind, placebo-controlled, phase 3 trial involving men with nonmetastatic castration-resistant prostate cancer and a prostate-specific antigen doubling time of 10 months or less. Patients were randomly assigned, in a 2:1 ratio, to receive apalutamide (240 mg per day) or placebo. All the patients continued to receive androgen-deprivation therapy. The primary end point was metastasis-free survival, which was defined as the time from randomization to the first detection of distant metastasis on imaging or death.

RESULTS

A total of 1207 men underwent randomization (806 to the apalutamide group and 401 to the placebo group). In the planned primary analysis, which was performed after 378 events had occurred, median metastasis-free survival was 40.5 months in the apalutamide group as compared with 16.2 months in the placebo group (hazard ratio for metastasis or death, 0.28; 95% confidence interval [CI], 0.23 to 0.35; P<0.001). Time to symptomatic progression was significantly longer with apalutamide than with placebo (hazard ratio, 0.45; 95% CI, 0.32 to 0.63; P<0.001). The rate of adverse events leading to discontinuation of the trial regimen was 10.6% in the apalutamide group and 7.0% in the placebo group. The following adverse events occurred at a higher rate with apalutamide than with placebo: rash (23.8% vs. 5.5%), hypothyroidism (8.1% vs. 2.0%), and fracture (11.7% vs. 6.5%).

CONCLUSIONS

Among men with nonmetastatic castration-resistant prostate cancer, metastasis-free survival and time to symptomatic progression were significantly longer with apalutamide than with placebo. (Funded by Janssen Research and Development; SPARTAN ClinicalTrials.gov number, NCT01946204 .).

SPARTAN, a phase 3 double-blind, randomized study of apalutamide (APA) versus placebo (PBO) in patients (pts) with nonmetastatic castration-resistant prostate cancer (nmCRPC)

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Background: Pts with nmCRPC are at risk for developing metastatic disease and cancer-specific mortality. There are no approved treatments for nmCRPC. APA is an orally administered next-generation androgen receptor inhibitor with antitumor activity in CRPC. SPARTAN evaluated the effects of APA on metastasis-free survival (MFS) in men with nmCRPC. Methods: Pts with nmCRPC and prostate-specific antigen doubling time (PSADT) of ≤ 10 mos were randomized 2:1 to APA (240 mg QD) or PBO. The primary end point was MFS, defined as the time from randomization to first radiographic distant metastasis (per blinded central review) or death. Secondary end points included time to metastasis (TTM), progression-free survival (PFS), time to symptomatic progression (SymProg), and overall survival (OS). Pts were eligible to receive study-provided abiraterone acetate plus prednisone after developing distant metastases. Second progression-free survival (PFS2, the time from randomization to disease progression or death after first treatment for metastatic CRPC) was also evaluated. Results: 1207 pts were randomized. Baseline PSADT was < 5 mos in both groups. APA decreased the risk of distant metastasis or death by 72% (HR = 0.28; 95% CI, 0.23-0.35; p < 0.0001), with a median MFS of 40.5 vs 16.2 mos in the PBO group. Secondary end points (TTM, PFS, and SymProg) were all significantly improved. At an interim analysis for OS, there was a trend favoring APA. At a median follow-up of 20.3 mos, 61% of APA and 30% of PBO pts were still on treatment. Rates of discontinuation due to adverse events were low in both groups (10.7% APA, 6.3% PBO). Mean baseline health-related quality of life scores were maintained with treatment, with no difference between groups over time. Of those whose disease progressed, 80% of PBO and 56% of APA pts received therapy for metastatic CRPC. PFS2 was significantly longer for APA vs PBO. Conclusions: APA significantly improved median MFS by 2 years in men with nmCRPC. APA also significantly increased TTM, PFS, SymProg, and PFS2. APA was associated with improved OS. These results support the addition of APA to androgen deprivation therapy in men with nmCRPC. Clinical trial information: NCT01946204.