Germline testing for men with prostate cancer: Need to broaden the indications in Europe?

383

Background: The clinical role of germline testing (GT) for prostate cancer (PC) is rapidly increasing due to the growing implications of precision medicine in metastatic disease, where genetic results can address eligibility for novel targeted treatments. Thus, ESMO and NCCN guidelines recommend GT for all metastatic PC individuals, whereas American testing criteria are more broad and include family history and other tumor features, such as high-risk disease, or intraductal or cribriform histology. Methods: We have retrospectively collected and analyzed clinical and genetic features of men with PC who underwent single-gene or multi-gene GT at some Swiss Institutions with expertise in hereditary cancers from July 2018 until October 2022. All patients (pts) have given written informed consent for research. Results: 109 men with PC underwent GT and received pre- and post-test counseling. Of these, 54 (50%) were metastatic, 34 (31%) had high-risk localized disease according to NCCN criteria, 7 (6%) presented cribriform or intraductal histology. A significant family history, as defined by current NCCN guidelines, was found in 79 (72%). 67 (61%) had no pathogenic (P) or likely pathogenic (LP) variants; 25 (23%) had a variant of unknown significance (VUS); 17 (16%) were found to have a P/LP variant in the following genes: BRCA2 (8), ATM (4), BRIP1 (1), FANCA (1), NBN (1), POT1 (1), TP53 (1). Among these 17 pts, the median age at diagnosis was 66 (45-80), 10 had metastatic disease, 5 had high-risk localized disease, 14 had a family history and 5 had a personal history of another cancer. Only 6 pts were <60 years old at the time of diagnosis. Cascade screening was offered to 16 families (94%). Conclusions: Our preliminary data support the increasing role of GT in PC and suggest the need to expand its indications. In this cohort, 7/17 (41%) of men with localized PC were found to carry P/LP variants and would not have met the criteria to undergo GT according to current European guidelines. GT may have treatment implications for metastatic PC pts whereas in early stage disease can inform cancer risk and screening for pts and their male and female relatives.

Phase 2, multicenter, randomized study of salvage radiation therapy +/- metformin for recurrent prostate cancer after radical prostatectomy (SAKK 08/15 – GETUG-AFU 34 PROMET trial)

353

Background: Pre-clinical and retrospective clinical data support an interaction of metformin (MET) and radiotherapy. Thus, MET may represent a cost-effective means to improve radiotherapy outcomes. We sought to investigate whether MET increases time to progression (TTP) when combined with salvage radiation therapy (SRT) in men with recurrent prostate cancer after radical prostatectomy (RP). Methods: Non-diabetic men with biochemical recurrence after RP were enrolled into an open label, randomized, phase 2 study in 17 hospitals in Switzerland, France, and Germany. The randomization (1:1) was stratified by Gleason score (<8 vs ≥8), surgical margin status (R0 vs R1), PSA at randomization (PSA > 0.5 vs ≤ 0.5 ng/mL), ADT use, and evidence of local recurrence. Following randomization, patients received either prostate bed SRT (70Gy) or prostate bed SRT (70Gy) + MET. MET 850mg PO QD was given for 4 weeks before SRT, then 850mg PO QD for 48 weeks. The primary endpoint was TTP. Secondary endpoints were progression-free survival, undetectable PSA under normal testosterone levels, 50% PSA response, clinical progression-free survival, time to further systemic therapy, prostate cancer-specific survival, overall survival, and adverse events (AE). The trial design was powered for a HR 0.65 with planned enrollment of 170 patients. The trial was prematurely closed by the sponsor due to financial reasons. Data is reported after patients reached a minimum follow-up of 12 months after SRT and corresponds to the final analysis. Results: A total of 111 patients were randomized (106 evaluable) between 10/2017 and 11/2020. The median PSA at randomization was 0.3 ng/mL (range, 0.03-1.5 ng/mL), 19 patients (17.9%) had Gleason ≥8, 54 (50.9%) pT3 disease, and 50 (47.2%) positive surgical margins. Twenty-four patients (22.6%) used short-term ADT. Trial arms were well balanced. At a median follow-up of 27.1 months (95% CI: 26.7-27.8), a total of 16 progression events occurred. The median TTP was not reached in either treatment arm. The hazard ratio adjusted by stratification factors was 1.25 (95% CI: 0.40-3.94; one-sided 80% CI: 2.05; log-rank p=0.62). Two-year TTP was 89% (95% CI: 76%-96%) in the SRT arm vs 82% (95% CI: 67%-91%) in the SRT + MET arm. No statistically significant differences were found for the secondary endpoints. Most common AE during treatment was grade 1-2 diarrhea (24.1% SRT vs 54.6% SRT + MET). Grade 2 and 3 AE (gastrointestinal and/or urinary) were 25.9% and 3.7% with SRT vs 34.5% and 7.3% with SRT + MET (p=0.41 and p=0.68), respectively. Conclusions: Adding MET to SRT did not result in a significant improvement in TTP in non-diabetic men with recurrent prostate cancer post-RP. Because of early trial closure and fewer than expected events, the trial may have been underpowered for this endpoint. Additional correlative studies will be pursued. Clinical trial information: NCT02945813 .

Pembrolizumab (pembro) plus enzalutamide (enza) for enza-resistant metastatic castration-resistant prostate cancer (mCRPC): KEYNOTE-199 cohorts 4-5

15

Background: KEYNOTE-199 (NCT02787005) is a multicohort phase 2 study. Cohort (C)4 (RECIST-measurable disease) and C5 (bone-predominant disease) consist of chemotherapy-naive patients (pts) with mCRPC treated with enza + pembro after progression with enza. Results for C4 and C5 presented. Methods: Pts with or without prior abiraterone had clinically meaningful response/benefit to enza followed by disease progression. Pts received pembro 200 mg Q3W with continuation of enza for up to 35 cycles or until progression/intolerable toxicity. Primary end point: ORR, blinded independent central review (C4). Secondary end points: DCR, PSA response rate (≥50% reduction), rPFS, OS, and safety (C4, C5); DOR (C4). Results: Of 126 pts (C4, 81; C5, 45), 107 discontinued, primarily due to progression. Median follow-up: 13.7 mo (C4, 11.8; C5, 18.6). ORR (95% CI) for pts with measurable disease was 12% (6-22) in C4; DCR for all pts: 51% (39-62) in C4 and 51% (36-66) in C5 (Table). Any grade/grade 3-5 treatment-related AEs occurred in 75%/26% pts in C4 and 69%/24% in C5. Two pts in C4 died of immune-related AEs (Miller Fisher syndrome and myasthenia gravis). Incidence of any grade/grade 3-4 rash (regardless of treatment relatedness) was higher than previously reported for individual agents (33%/6%). All except one pt (grade 3 treated with IV steroids) were treated with oral/topical steroids or had no intervention. Conclusions: Addition of pembro to enza following enza resistance showed modest antitumor activity in pts with RECIST-measurable and bone-predominant mCRPC. Combination had manageable safety and is being evaluated in a phase 3 trial. Clinical trial information: NCT02787005. [Table: see text]

Consensus statement on circulating biomarkers for advanced prostate cancer

299

Background: The need for validated circulating biomarkers is well recognised in advanced prostate cancer (PCa). Circulating biomarkers evaluating plasma cell-free nucleic acids and circulating tumour cells are being investigated for their clinical utility. There has been a lack of consensus with regards to analyses, reporting and clinical effectiveness of these biomarkers. A consensus meeting was held to address these issues. Methods: A multi-disciplinary panel comprising 18 international prostate cancer experts (including surgeons, medical and radiation oncologists) were consulted prior to the consensus meeting. Four key areas relating to the field of circulating biomarkers were deemed important for discussion: 1) The current utility of circulating biomarkers in 2017; 2) The clinical needs for circulating biomarkers in PCa; 3) The most pressing blood-based molecular assays required; and 4) The steps necessary for developing circulating biomarkers. Using a modified Delphi process, 50 consensus questions were pre-defined for the panel to answer by voting anonymously but publicly at the consensus meeting. Results: A consensus was declared (i.e. ≥ 75% of panellists who did not vote ‘unqualified’ or ‘abstain’ chose the same opinion) in 12/50 (24%) questions. A further 8/50 (16%) of replies were close to reaching consensus (≥ 60% of panellists choosing the same answer). The panel agreed that there is a very high and urgent unmet need for predictive biomarkers, with consensus that DNA repair biomarkers in particular are needed urgently. Metastatic PCa was identified as having the highest clinical need for development of biomarkers to measure response and as surrogate endpoints. Panellists unanimously voted that reproducibility validation studies are of paramount importance. The consensus panel also predicted that cfDNA will impact practice by 2020. Conclusions: This expert consensus identified the need for clinical trials of validated circulating biomarkers to develop predictive, response and surrogacy assays. These could have major clinical and healthcare economic implications, minimizing over-treatment and allowing the delivery of more precise patient care.

SAKK 08/15-promet: Multicenter, randomized phase II trial of salvage radiotherapy +/- metformin for patients with prostate cancer after prostatectomy

TPS157

Background: Salvage radiotherapy (SRT) is as a potentially curative treatment for prostate cancer (CaP) patients presenting biochemical relapse after radical prostatectomy (RP). Metformin is a well-known antidiabetic drug that has demonstrated anti-cancer and radio-sensitizing effects. We aim to study whether metformin combined with SRT will improve cancer control by prolonging time to progression (TTP). Methods: This is a multicenter, randomized (1:1) phase II trial of SRT (70Gy/35fr to the prostate bed) with or without metformin (850mg BID for 52 wks) (NCT02945813). Metformin 850mg q.d. is started 4 wks prior to SRT. Stratification variables include Gleason score, PSA at randomization, surgical margin status and ADT use (allowed if PSA > 0.5, R0, post-RP PSA-DT < 6 mos or pT3b). Major eligibility criteria include: histologically proven CaP adenocarcinoma pT2a-3b, pN0 or cN0, M0; RP > 12 wks before registration; PSA progression after RP defined as 2 consecutive rises with final PSA > 0.1 ng/mL or 3 consecutive rises; and PSA ≤ 2 ng/mL within 14 days prior to registration. A sample size of 170 patients (85 per arm) is planned based on the primary endpoint TTP. Using a type I error of 5% and a power of 80%, 62 events are needed to show superiority of the treatment arm under the alternative hypothesis that the hazard ratio (HR) is 0.65 (TTP at 18 mos of 80% in the control arm vs. 86.5% in the treatment arm). All efficacy endpoints will be analyzed based on the full analysis population. The treatment effect will be assessed using Cox regression with the treatment arm as independent variable and the stratification factors as strata. Correlative studies including prostate tissue, blood (metabolic parameters), saliva and feces (microbiota) will be performed. Conclusion: Centers in Switzerland, Germany and France (GETUG) will recruit patients for this study. If positive, these results could help elucidate the role of metformin in CaP and determine the design of a subsequent phase III trial. Clinical trial information: NCT02945813.

A phase Ib/II dose-escalation study evaluating triple combination therapy with a BRAF (encorafenib), MEK (binimetinib), and CDK 4/6 (ribociclib) inhibitor in patients (Pts) with BRAF V600-mutant solid tumors and melanoma

9518

Background: The benefits of BRAF + MEK inhibition (dual combo) in pts with BRAF V600-mutant ( BRAFV600) melanoma are known. Preclinical data supports inhibiting CDK 4/6 and BRAF + MEK (triple combo) to improve antitumor activity. We report safety and preliminary efficacy from a phase 1b/2 study (NCT01543698) of encorafenib (ENCO; a selective BRAF kinase inhibitor), binimetinib (BINI; a MEK inhibitor), and ribociclib (RIBO; a CDK 4/6 inhibitor). Methods: Phase 1b of this open-label, multicenter study enrolled pts with confirmed BRAFV600advanced solid tumors. Escalating doses of RIBO 100 mg-600 mg QD for 3 wk on/1 wk off were administered with ENCO 200 mg QD + BINI 45 mg BID in successive cohorts (6 pts each) until the maximum tolerated or recommended phase 2 dose (RP2D) was reached. Due to potential pharmacokinetic interactions with RIBO, the ENCO dose was lower than the dual combo RP2D (450 mg QD). Dose escalations followed an adaptive Bayesian model. In phase 2, the triple combo was tested in pts with BRAFV600melanoma naïve to prior BRAF inhibitor treatment; the primary endpoint was objective response rate (ORR) per RECIST v1.1. Results: In phase 1b (n = 21), no dose-limiting toxicities were reported and the triple combo RP2D was ENCO 200 mg QD + BINI 45 mg BID + RIBO 600 mg QD. ENCO AUC was slightly lower than at the dual combo RP2D. In phase 2 (n = 42), 59.5% pts had an ECOG PS of 0 and 43% of pts had elevated lactate dehydrogenase. The most common (≥5%) grade 3/4 toxicities were neutropenia (26.2%), increased alanine transaminase (14.3%), diarrhea (7.1%), and anemia (7.1%). Ten pts (23.8%) discontinued treatment due to an AE, of which 4 were increased transaminases. The confirmed ORR was 52.4%, including 4 complete responses, 18 partial responses, and 15 pts with stable disease. Median duration of exposure in phase 2 was 9.1 mo (range, 0.0-21.6). Median progression-free survival was 9.0 mo (95% confidence interval, 7.0-11.1). Conclusions: Triple therapy with ENCO + BINI + RIBO in this small trial of pts with high disease burden was associated with responses in over half of pts and some evidence of increased toxicity. Clinical trial information: NCT01543698.

A phase I study to assess the safety, pharmacokinetics (PK), pharmacodynamics (PD) and antitumor activities of BAL101553, a novel tumor checkpoint controller (TCC), administered as 48-hour infusion in adult patients with advanced solid tumors

TPS2602

Background: BAL101553 (prodrug of BAL27862), is a novel TCC that promotes tumor cell death by modulating the spindle assembly checkpoint. BAL27862 has shown potent antitumor activity in diverse preclinical tumor models, including models refractory to standard therapies. In a completed Phase 1 study using 2-h IV infusions (Days 1, 8, 15, q28d, NCT01397929 , CDI-CS-001, Lopez et al. JCO 34, 2016 suppl; 2525) dose-limiting vascular effects were observed and appeared Cmax related. The recommended Phase 2 dose for 2-h IV BAL101553 is 30 mg/m2. Vascular toxicity was not observed in an ongoing study with oral BAL101553 (NCT02490800, CDI-CS-002) at daily doses up to 30 mg (QD). Preclinical data suggest that antiproliferative effects of BAL101553/27862 are driven by exposure (AUC); thus vascular toxicity and antitumor activity are mediated by different PK drivers. BAL27862 has a half-life of ~15 h. Based on PK-modeling, extending the infusion from 2 h to 48 h was expected to result in ~4-fold higher AUC at a given Cmaxlevel and thereby improve the therapeutic window. Methods: This is an ongoing multicenter, open-label, Phase 1 dose-escalation study (NCT02895360, CDI-CS-003/SAKK67/15) using a 3+3 design to determine the MTD, characterize dose-limiting toxicities and assess the PK, PD and antitumor activities of 48-h infusions of BAL101553 in consecutive 28-day cycles at a starting dose of 30 mg/m2 administered on Day 1, 8 and 15 (q28d). The dose escalation scheme foresees up to ~ 50% dose increments depending on observed toxicities. During cycle 2, patients receive 7 days oral (QD) BAL101553 (Day 15–21) instead of the weekly IV infusion to assess absolute oral bioavailability. Patients with histologically-confirmed advanced or recurrent solid tumors are eligible for enrollment. Adverse events are assessed using CTCAEv4; tumor response by RECIST 1.1 (every 2 cycles). PD assessments include optional tumor biopsies and circulating tumor cells. PK profiles are assessed during the first 2 cycles. Two dose cohorts (30 and 45 mg/m2) have completed without DLTs or signs of vascular toxicity. Clinical trial information: NCT02895360.

Interrogating metastatic prostate cancer treatment switch decisions

296

Background: Increased availability of treatment options in CRPC requires improved biomarkers to optimize decision making for therapeutic sequencing. Despite evidence for the value of CTCs in assessing prognosis and response to treatment, their use in clinical practice is not widely implemented. Clinicians rely on PCWG2 criteria based on PSA, clinical and radiological criteria although these are only inconsistently used in clinical practice. We evaluated the trends for clinical decision-making by physicians treating CRPC. Methods: An online questionnaire was distributed to physicians treating PC from the UK, Switzerland and Australia. Questions on clinical practice, familiarity with progression criteria, use of CTCs and clinical-decision making were formulated. Results: 111 participants replied. Most (84.7%) were oncologists treating ≥ 50 patients per year (65.3%). Although only 39.6% usually used PCWG2 in clinical practice, 74.5% considered PSA, bone scans and CT to be useful for monitoring disease. 55.6% considered PSA to be an important biomarker. A minority were able to identify PSA (41.4%) and bone scan (39.4%) progression criteria by PCWG2. On average, more physicians discontinued cabazitaxel (28%) than docetaxel (10.4%) before cycle 4. Similar number of cycles were given to bone only disease compared to RECIST evaluable patients. Clinical progression was most important for switching treatment for most physicians (90.5%), followed by RECIST (71.6%), bone scan (47.7%), CTC (23.2%) and PSA (21.1%). The main challenge associated with the use of CTCs was the access to technology (84.7%). Most respondents (92%) would not stop therapy with rising PSA but falling CTC counts; most (88.8%) would not stop with declining PSA but rising CTCs. Although 50% acknowledged the prognostic value of CTCs, only 33% would use them to guide decision-making. Conclusions: A significant number of physicians discontinue treatment before 12 weeks. Most physicians rely on clinical progression for decision-making. Knowledge of PCWG2 response and progression criteria is generally suboptimal. Greater physician awareness, access to technology and further evidence and will be required for the implementation of CTCs as a routine biomarker in CRPC.

The oral CYP17-Lyase (L) inhibitor VT-464 in patients with CRPC

187

Background: VT-464 is an oral, non-steroidal inhibitor of CYP17-L and an antagonist of androgen receptor (AR) variants F876L and T877A which are associated with resistance to enzalutamide (ENZ) and abiraterone/prednisone (AA), respectively. INO-VT-464-CL-001 is a Phase (Ph) 1/2 study of VT-464 in treatment-naïve (TN) and treatment-failure (TF) patients with CRPC. Results are reported for Ph 1 (TN patients) and early results from Ph 2 patients. Methods: Phase 1: safety, tolerability, PK and initial efficacy (PSA and steroid concentrations) in M0 and M1 TN patients in escalated dose-cohorts from 50 to 600 mg bid in 28-day continuous dosing cycles. Phase 2: preliminary efficacy in M0 and M1 TN and TF (post-AA, -ENZ, and/or CHEMO) patients at 450 mg bid. Results: In Ph 1, 26 TN patients received VT-464 at 50 mg bid (n=1), 100 mg bid (n=1), 200 mg bid (n=4), 300 mg bid (n=8), 450 mg bid (n=9) and 600 mg bid (n=3) with 2 patients currently on study (15 and 29 months). Another 10 TN patients received VT-464 in Ph 2 at 450 mg bid. Most Ph 1 adverse events (AEs) were grade 1 or 2 and not considered drug related. There were 18 grade 3 AEs and 1 grade 5 AE considered not related to study drug, plus 4 grade 3 AEs (vasovagal/syncope) considered at least possibly related. For a single oral 450 mg dose, t½ was 6.8±0.8h (mean±SEM), Cmax was 8.6±1.2uM and Tmax was 3.4±0.7h. 19 of 26 Ph 1 and Ph 2 TN patients who received from 300 to 600 mg bid had PSA responses (6 PSA30%, 2 PSA50% and 1 PSA90% response). Preliminary PSA responses in Ph 2 TF patients included a PSA90% response in a prior-ENZ pre-chemo patient and a PSA50% response in a prior-ENZ and -chemo patient. No mineralocorticoid excess syndrome (MES) or changes in ACTH response or LFTs were observed. Plasma testosterone concentrations were reduced to near or below the limit of quantification in most patients at ≥ 450 mg bid, with normal progesterone and cortisol concentrations. No supplemental steroids were used. Conclusions: Clinical results at the doses evaluated support VT-464 CYP17 L-selectivity. The PSA50% and PSA90% responses in 2 of 7 prior Xtandi patients, combined with a lack of MES despite no supplemental steroids, warrants further investigation in the ongoing Ph 2 study, particularly in prior ENZ and AA patients. Clinical trial information: NCT02012920.

Predicting positive bone marrow biopsies (BMBs) in patients (PTS) with advanced prostate cancer (APC)

180

Background: Advanced prostate cancer (APC) is a molecularly heterogeneous disease, with evidence of clonal evolution that could be responsible for resistance to treatment. About 90% of patients (pts) with APC have bone metastases. The acquisition of a bone marrow biopsies (BMBs) is a safe and feasible technique for obtaining tissue, with a low rate of complications. We hypothesized that pre-biopsy clinical variables may increase the success rate of BMBs in APC. Methods: Standard BMBs of the iliac crest were performed in APC pts between October 2011 and June 2013. All pts signed ethics approved consent. In the control cohort (n=10) BMBs were collected in pts with normal CT and bone scan appearance. Minimum, maximum, and mean Hounsfield Units (HU) of the iliac crest on pre-biopsy CTs were determined. Clinical and laboratory variables were collected from the electronic record system. Biopsies were defined as containing 50 or more or 1 to 50 malignant cells or none (negative). Univariate analysis was performed to determine variables associated with biopsy positivity with 50 or more cells. For variables with p value<0.1, the optimal cut-off point was determined by ROC curve analysis. A multivariate analysis with optimal cut-off points was then performed. Results: A total of 71 BMBs were performed in 57 pts. None of the control biopsies in pts with normal CT and bone scan (10 of 10) contained tumor. A total of 46 of 61 BMBs (75.4%) were positive. 38 of 61 (62.3%) contained 50 or more cells. Prior treatments were docetaxel in 57 (79.2%) and abiraterone in 42 (58%) pts. Bisphosphonates had been used in 21 (28.8%) pts. The significant variables on univariate analysis were ALP more than or equal to 200 IU/L (p=0.059), prostate-specific antigen (PSA) more than or equal to 225 ng/mL (p=0.008), lactate dehydrogenase (LDH) more than or equal to 200 IU/L (p=0.09), mean HU more than or equal to 125 (p=0.000) and maximum HU more than or equal to 550 (p=0.001). These factors were tested in multivariate analysis. Only PSA and mean HU were significant in multivariate analysis. The combined PSA and mean HU score had an ROC AUC of 0.79. Conclusions: A combination of PSA and mean HU on CT could assist physicians in selecting APC patients/ iliac crest site more likely to have a positive BMB. Prospective evaluation is ongoing in a validation set.

A prognostic score for patients with metastatic castration-resistant prostate cancer treated with abiraterone acetate post chemotherapy

70

Background: We aimed to establish a simple prognostic score for men with mCRPC treated with abiraterone following docetaxel and explored incorporation of the neutrophil/lymphocyte ratio (NLR), a marker of host inflammation with prognostic value in many solid tumors. Methods: To develop the model, clinical and laboratory factors for 185 men treated at Royal Marsden were included in a univariable Cox regression analysis. Statistically significant variables were dichotomized using an optimal cut-off chosen by selecting the highest c-index among three potential cut-offs with high Hazard Ratios (HR). All significant variables in univariable analysis were analyzed using multivariable Cox analysis. One risk point was assigned for each variable with a P value of <0.05 in multivariable analysis and the risk points were used to establish three prognostic groups of similar prevalence. The validity of the model is being examined using the large data-set from the abiraterone registration trial (COU-AA-301). Results: Median age was 69 years, 41% had both bone and lymph node metastases (BLN), 15% had visceral disease. Involvement of BLN or visceral disease (HR 1.6, P=0.013), ALP >2.0 x ULN (HR 1.7, P=0.005), LDH >1.5 x ULN (HR 3.4, P<0.001), Hgb <12 g/dL (HR 2.1, P<0.001), and NLR >5 (HR 1.5, P=0.033) were associated with worse OS in the multivariable analysis. Outcomes for three risk groups using these 5 factors are presented in the table. The c-index was 0.73 (95% CI 0.65 - 0.80) for the prognostic score. Patients with NLR >5 at baseline and whose NLR was ≤5 within four weeks of treatment also had longer median survival (15.1 months) than those with NLR >5 at baseline that remained high (median OS 7.6 months, HR 0.48, 95% CI 0.25-0.93, P=0.029). Conclusions: This initial simple risk score provides good prognostic and discriminatory accuracy for men with mCRPC. Data from the validation cohort will be presented. [Table: see text]

A first-in-human study of the oral selective androgen receptor down-regulating drug (SARD) AZD3514 in patients with castration-resistant prostate cancer (CRPC)

4511

Background: AZD3514 is a first in class, orally bio-available drug that inhibits androgen-dependent and –independent androgen receptor (AR) signaling through two distinct mechanisms; inhibition of ligand-driven nuclear AR translocation and down-regulation of AR levels. Methods: A rolling six design was employed initially using a once a day (QD) schedule (A). PK assessments led to a change to twice daily (BD) dosing (B) to increase exposure. PK profiles were studied over 96 hours after a single dose and over 24 hours at start of/following 21 days continuous dosing. PD analyses included PSA and CTC quantification. Results: 49 CRPC patients (pts) have been treated with escalating doses of AZD3514 (A 35 pts, B 14 pts). Starting doses were 100 mg (A) and 1000 mg (B). The AZD3514 formulation was switched from capsules to tablets at 1000mg (QD). 2000mg BD was considered non-tolerable due to multiple grade 2 toxicities (nausea [N], vomiting [V], fatigue). No adverse events (AEs) met the DLT definition. The most frequent drug-related AE’s were N; G1/2 36/49 (73%), G3 2/49 (4%) and V; G1/2 24/49 (49%) & G3 3/49 (6%). N/V were managed with oral anti-emetics. Dose proportional increases in plasma concentrations were observed following a single dose. Geometric mean (%CV) Cmax and AUC at MTD were 9,608 (38.5) ng/mL and 61,734 (40.6) ng.hr/mL, respectively. Compared with single dose continuous dosing led to a mean decrease of 26% in exposure. Maximum PSA and CTC declines are summarized below. Objective soft tissue responses per RECIST1.1 were observed in 2/26 (8%) pts. One pt with abiraterone resistant disease remained on study for 19 months. At 6 and 12 months 21 (43%) and 8 (16%) pts remained on study without evidence of bone or soft tissue progression, respectively. Conclusions: AZD3514 has antitumor activity in patients with advanced CRPC. Clinical trial information: NCT01162395. [Table: see text]

First-in-human phase I study of EZN-4176, a locked nucleic acid antisense oligonucleotide (LNA-ASO) to androgen receptor (AR) mRNA in patients with castration-resistant prostate cancer (CRPC)

5052

Background: EZN-4176 is a third generationLNA-ASO that binds the ligand binding domain of AR mRNA resulting in full length AR mRNA degradation and decreased AR protein expression. Methods: Patients (pts) (performance status ECOG≤1) with progressing CRPC were eligible; prior abiraterone and enzalutamide treatment were allowed. EZN-4176 was administered as a weekly (QW) one-hour intravenous infusion. The starting dose was 0.5 mg/Kg with a 4-week dose-limiting toxicity (DLT) period. After determination of the DLT and the maximum tolerated dose (MTD) for weekly administration, a fortnightly schedule (Q2W) was initiated; a 3+3 modified Fibonacci dose escalation design was pursued. PD studies evaluated AR expression in tissue utilizing antibodies to the amino and carboxy-termini of the AR. Results: 22 pts were enrolled (median age 70.6 years, range 59 – 84 years). One pt was treated with the Q2W schedule. Two DLTs (G3/G4 ALT/AST elevation) occurred at 10 mg/Kg, which was therefore identified as the MTD for the weekly schedule. Multiple pts treated at 6.5 and 10 mg/Kg (5/9 pts, 55%) developed ≥G2 ALT and/or AST elevation after the first cycle requiring dose reduction and treatment delay. The most frequent adverse events (AEs) all-grades were fatigue (21/22 pts, 95.4%), nausea (10/22 pts, 45.4%), constipation (8/22 pts, 36.3%), AST (8/22 pts, 36.3%) and ALT (10/22 pts, 45.4%) elevation. The most frequent G3/4 AEs were AST (4/22 pts, 18.1%) and ALT (5/22 pts, 22.7%) elevation. Maximum PSA and circulating tumor cells (CTCs) declines are summarized below. There were no objective soft tissue responses. PD studies did not document any knockdown of AR expression Conclusions: EZN-4176 has limited antitumour activity in CRPC at its MTD for weekly administration. Safety, PK, PD and efficacy data will be presented. Clinical trial information: NCT01337518. [Table: see text]

Final results of the phase I trial of niraparib (MK4827), a poly(ADP)ribose polymerase (PARP) inhibitor incorporating proof of concept biomarker studies and expansion cohorts involving BRCA1/2 mutation carriers, sporadic ovarian, and castration resistant prostate cancer (CRPC)

2513

Background: Niraparib(N) is an oral, potent PARP1/2 inhibitor that induces synthetic lethality in BRCA1/2 deficient tumors. PARP is also implicated in transcription regulated by the androgen receptor (AR) and rearranged ETS genes; key targets in CRPC. Methods: Dose-escalation was enriched for BRCA1/2mutation carriers (BRCA-MCs). Two MTD expansion cohorts were undertaken in patients (pts) with sporadic high grade serous ovarian cancer (HGSOC) and CRPC. In CRPC pts, archival tissue and circulating tumor cells (CTC) were analyzed for PTEN deletion and ETS gene rearrangements. Results: 100 pts [ovary (49), CRPC (23), breast (12) others (16)], received N at 10 dose levels: 30mg to 400mg daily (od), continuously. Grade (G) 4 thrombocytopenia was dose limiting at 400mg od; MTD was established at 300mg od. Drug-related toxicities were G1-2 reversible anemia (48%), fatigue (42%), nausea (42%), thrombocytopenia (35%), anorexia (27%), neutropenia (24%), constipation (23%), and vomiting (20%). PKs were dose proportional with a mean elimination t1/2of 40 hours. Peripheral blood mononuclear cells had >50% PARP inhibition from 80 mg od. gH2AX foci formation, a marker of DNA damage, was seen in CTCs. Antitumor activity occurred from 60mg od with RECIST and/or CA125 partial responses (PR) in 9/20 (45%) BRCA-MC ovarian cancer pts and 2/4 (50%) BRCA-MC breast cancer pts. Platinum-sensitive vs resistant BRCA-MC HGSOC response rate was 60% vs 33% with median time for responding pts of 429 and 340 days, respectively. In sporadic HGSOC, there were 2/3 PRs in platinum-sensitive pts, and 3/20 PRs plus 4/20 stable disease (SD) >16 weeks in platinum resistant pts. In CRPC, symptomatic benefit and SD >6 months (median 9 months) was seen in 9/21 (43%) pts treated at MTD. CTC declines of >30% (median 80%; range 36%-92%) were observed in 7/10 (70%) pts with evaluable CTC counts (≥5 cells/ 7.5mL blood). Conclusions: Niraparib was well tolerated and has promising antitumor activity in BRCA-MCs, sporadic HGSOC and CRPC. Clinical trial information: NCT0074902.

A phase I/II study of cabazitaxel (Cbz) combined with abiraterone acetate (AA) and prednisone (P) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) whose disease has progressed after docetaxel (D) chemotherapy: Preliminary results

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Background: Both Cbz and AA have demonstrated significantly improved survival in randomized Ph 3 studies in pts with mCRPC and progressive disease after D treatment. Cbz and AA have established non-overlapping adverse event (AE) profiles. A Ph 1/2 study was initiated to investigate the combination of Cbz + AA for the treatment of mCRPC (NCT01511536). Methods: Pts with progressive mCRPC after D were enrolled. The primary objectives were to determine the maximum tolerated dose (MTD) and dose-limiting toxicities (DLTs) of Cbz + AA (Ph 1), and the PSA response rate (RR) with this combination (Ph 2). Secondary endpoints included AEs, pharmacokinetics (PK) and efficacy. All pts received oral AA 1000 mg QD and P 5 mg BID. In Ph 1, pts received 1 of 2 dose levels (DL) of Cbz (20 and 25 mg/m2 IV Q3W) according to a 3+3 design. A 2-cycle DLT observation period was used. Here, we report results of Ph 1. Results: Ten pts were enrolled in Ph 1; 9 were evaluable: 3 at DL1 and 6 at DL2 completed 2 cycles without DLTs (total number of cycles = 46). In general, AEs were Grade (Gr) 1/2; the most frequent all-Gr AEs by pt cycle were asthenia (39%), diarrhea (37%; Gr 3 in 1 pt), back pain (26%), nausea (20%), constipation (20%), anemia (17%), decreased appetite (17%) and fatigue (15%; Gr 3 in 2 pts). In the safety population, 0/3 pts at DL1 and 2/7 pts at DL2 experienced Gr 3–4 neutropenia. The MTD was established at the full approved doses of both drugs (Cbz 25 mg/m2/AA 1000 mg). In 6 pts evaluable for PK (DL1 and DL2), median Cbz clearance (coefficient of variation %) was similar at cycle 1 (Cbz alone: 28.9 L/h/m2 [11%]) and cycle 2 (Cbz + AA coadministration: 28.6 L/h/m2 [42%]). In 9 evaluable pts, 55% PSA RR was observed. Conclusions: In this Ph 1 study, Cbz in combination with AA appeared to have a manageable safety profile. Gr 3–4 neutropenia was observed in 2 of 10 patients. Daily AA treatment did not affect Cbz clearance; Cbz exposure was comparable to previous studies of Cbz + P treatment. The Ph 2 portion is ongoing at the established MTD. Detailed safety, PK and preliminary efficacy data (Ph 1) will be presented. Clinical trial information: NCT01511536.

Response to cabazitaxel in CRPC patients previously treated with docetaxel and abiraterone acetate

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Background: Cabazitaxel, which is a tubulin-binding chemotherapy, and the CYP-17 androgen biosynthesis inhibitor abiraterone acetate (AA) are both approved for patients with metastatic castration resistant prostate cancer (CRPC) following docetaxel chemotherapy. Recent preclinical data suggest that taxanes impact AR signalling and could imply cross-resistance between new AR targeting treatments and taxane chemotherapy. The aim of this study is to evaluate the antitumor activity of cabazitaxel after AA. Methods: We retrospectively evaluated antitumor activity of cabazitaxel in patients (pts) with metastatic CRPC and progressive disease after docetaxel and AA. Radiological response by RECIST, PSA response by PCWG2 criteria and symptomatic benefit were examined. Results: 89 pts were treated with third-line cabazitaxel, after docetaxel (median 8 cycles; range: 4-12), and AA (median duration of treatment 4.8 months, range: 1-55 months). At cabazitaxel initiation median age was 68 years (range: 53-83), ECOG performance status was 0 or 1 in 70% of pts, and median PSA was 309 ng/ml (range: 3.75-9150). Bone, lymph node and visceral metastases were present in 80 pts (89%), 37 pts (41%), and 12 pts (13%) respectively. An average of 6 cycles of cabazitaxel (range 1-15) were administered. All pts had PSA data available and 44 (49%; 95% CI 39-60%) had a 50% or greater PSA decline. In the 35 pts with RECIST evaluable disease, 7 (20%; 95% CI 8-37%) had a partial response. Conclusions: In men with metastatic CRPC cabazitaxel appears to retain activity in the third-line setting following docetaxel and AA.

A pharmacokinetic (PK) pharmacodynamic (PD) driven first-in-human study of the oral class I PI3K inhibitor CH5132799, in patients with advanced solid tumors

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Background: The phosphatidylinositol 3-kinase (PI3K) pathway is a promising target in cancer. CH5132799 is a novel PI3K inhibitor, selectively inhibiting class I PI3Ks (α, β, δ and γ) with no inhibition of class II and III or mTOR, and with potent antitumor activity in preclinical studies (Tanaka et al, Clin Cancer Res; 17; 3272-81, 2011). First-in-human study objectives were determination of maximum tolerated dose (MTD), safety/tolerability, PK/PD and clinical activity (RECIST). Methods: A 3+3 dose escalation design was used. The initial dosing schedule of CH5132799(schedule A) was once a day (QD). Due to a relatively short half-life, a twice a day (BID) schedule (schedule B) was introduced. PK profiles were studied over 72 hours. PD analyses included quantification of various phosphoproteins in platelet rich plasma (PRP). Tumor assessments were performed at baseline and cycle 3 day 1 (C3D1) and FDG-PET scans at baseline, C1D8 and C3D1. Results: 29 patients (pts) with a variety of solid tumors have been treated (A 23 pts, B 6 pts, the most common tumors were breast, oesophageal, colorectal and ovarian). The starting doses were 2 mg (A) and 48 mg (B). The current doses being explored are 96 mg (A) and 72 mg (B). The most frequently reported drug-related AEs were Grade 1/2 diarrhea, nausea, fatigue, anorexia and anemia. 1 DLT (Grade 3 elevated LFT) was observed in a hepatocellular carcinoma pt at 48 mg BID. MTD has not yet been determined. The preliminary mean ±SD Cmax and AUC at 96 mg QD were 202±129 ng/ml and 1407±935 ng·hr/ml respectively, which is consistent with an efficacious exposure based on preclinical models. Some patients achieved the expected exposure at over 32 mg. From single dose of 48mg there was a reduction of phosphorylation of AKT in PRP after treatment, consistent with pathway modulation. A patient with clear cell ovarian cancer and a PIK3CA mutation treated at 48 mg BID showed >50% decrease in SUV on a PET scan at C1D8 and a 75% decrease in CA-125 at C2D1. 5 pts exhibited SD (>8 weeks). Conclusions: CH5132799 is well tolerated either QD ≤96 mg or BID ≤48 mg. Dose-escalation continues and updated safety/efficacy/PK/PD data will be presented.

Survival in metastatic castration resistant prostate cancer (mCRPC) trial participants

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Background: Median overall survival (mOS) in patients (pts) with metastatic prostate cancer progressing despite castrate levels of testosterone (mCRPC) was 13-16 months (m) in the pre-docetaxel era. These data, obtained from clinical trials, were used to construct currently available prognostic nomograms. We hypothesise that these models no longer reflect survival. Pts and physicians urgently require updated prognostic data on which to base management decisions. Methods: Pts with mCRPC treated on phase I-III trials at our institution were identified and data retrospectively collected. Predicted survival by Halabi and Smaletz nomograms were compared to calculated survival using Kaplan-Meier analysis. Cox model multivariate (MV) analysis used variables at referral, including performance status (PS), Gleason (GS), prostate specific antigen (PSA), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), hemoglobin (Hb), visceral disease and albumin. Results: 423 pts with CRPC treated between 2003 and 2011 were included. At diagnosis median age was 62 years (y; 41.8 – 82.7); 226 (53.4%) had metastatic disease. Median interval from diagnosis to CRPC was 2.7y (0.2 – 21.7). At referral 248 pts (58.6%) were chemotherapy-naïve. Halabi and Smaletz models predicted mOS in chemo-naïve pts of 21m and 18m respectively, however the observed mOS was 32m (95%CI 28 – 38). Survival from CRPC was 43m (CI 37 – 46) and 39m (CI 34 - 44) in pre- and post-chemo pts, respectively. Conclusions: Despite aggressive disease characteristics, our pts lived significantly longer than predicted by current nomograms. MV analysis confirmed the importance of several previously identified prognostic factors. Survival data from this large cohort of CRPC pts should encourage men considering clinical trial participation. Previously developed nomograms no longer accurately predict survival.

Durable radiologic and clinical disease stability beyond PSA progression in patients with metastatic castration-resistant prostate cancer (mCRPC) treated with abiraterone acetate (AA)

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Background: AA, a potent oral CYP17A1 inhibitor is approved for treatment of mCRPC with a survival advantage of 4.9 months. In clinical practice, response evaluation remains challenging for pts with mCRPC. CTC conversion from CTC ≥ 5 to CTC < 5 with treatment predicts for improved overall survival in mCRPC. We hypothesized that pts continue to have durable disease stability beyond PSA progression on AA. Methods: Prostate Specific Antigen (PSA) responses, radiological responses and CTC conversion rates were retrospectively analysed in pts treated on AA at our institution. CTCs, PSA and imaging were obtained at predefined time points during these studies. Radiological and PSA progression were defined by standard Prostate Cancer Working Group Criteria II. Clinical progression consisted of worsening disease related pain, skeletal events or declining performance status.Pearson’s chi-squared test and the Kaplan-Meier method were used for this analysis. Results: 141 patients [ECOG Performance Status 0-2; Median Age: 69.7 (range 44.7-87.1); 85 post-docetaxel, 56 pre-docetaxel] received AA. The median duration of clinical and radiological stable disease (SD) was 16.8 months (n=55) and 5.6 months (n=75) in patients with a baseline CTCs count of ≤ 5 cells/7.5mls and ≥ 5 cells/7.5 mls respectively. In the 105 patients with documented PSA progression on AA there was a median 5.7-month delay in detecting radiological and/or clinical progression (95% CI: 4.2, 8.4; range 0.3, 35.6 months). Radiological and clinical SD of ≥ 1 year, ≥ 2 years and ≥ 3 years on AA was observed in 43/141 (30.5%), 21/141 (14.9%) and 12/141 (8.5%) respectively. Conclusions: Radiological and clinical disease stabilization beyond PSA progression is maintained in a high proportion of mCRPC patients treated with AA. Future studies should evaluate whether continued AA treatment beyond PSA and radiological progression can impact outcome.

Sarcopenia and altered body composition following abiraterone acetate (AA) and corticosteroid (C) treatment in men with castration-refractory prostate cancer (CRPC)

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Background: Sarcopenia, or skeletal muscle wasting, is an independent prognostic factor in advanced malignancy (Prado Lancet Onc 2008). Decreased muscle and increased fat are recognized side effects of androgen deprivation therapy. AA is a CYP17 inhibitor administered with corticosteroids (C), approved for treatment of advanced CRPC. AA reduces circulating androgens to ‘super-castrate’ levels; we hypothesized that AA + C would impact body composition. Methods: We retrospectively evaluated 54 CRPC pts treated on a Phase I/II trial. Pts received AA alone followed by combination AA + C on biochemical progression. CT scans at baseline, on AA alone and on AA + C were analyzed. Cross-sectional areas of fat and muscle were measured on 3 consecutive images at L4 using OsiriX 4.0. Muscle area was used to calculate skeletal muscle index (SMI); sarcopenia was defined as SMI <52.4 cm2/m2. Data were analyzed using t-tests and Kaplan-Meier analysis with overall survival (OS) measured from day 1 of AA. Results: Median duration on AA alone was 7.4 months (m; range 1.4-37.5); median duration on concurrent AA + C was 7.4m (range 0.9-46.2). Body composition did not change between two pre-treatment scans (n=29; median 3m apart). On AA alone there was a decrease in total fat (-8.5%, p=0.0001), visceral fat (-9.8%, p=0.0015) and muscle mass (-3.9%, p=0.0023) with a significant decrease in mean body mass index (BMI; -3.4 %, p=0.0118). Conversely AA + C was associated with increased total fat (+15.1%, p<0.0001) and visceral fat (+21.4%, p<0.0001) but no further change in muscle mass. Mean BMI significantly increased on the addition of C, returning to baseline levels (p< 0.0001). Overall, 13 pts (24%) were sarcopenic prior to commencing AA compared to 22 (41%) at the end of treatment. Pts who were sarcopenic at baseline had significantly reduced OS: 26.1m (95%CI 16.6 – 41) vs 46.5m (95%CI 28.6 – 57.5, p=0.0253). Conclusions: Treatment with AA alone resulted in decreased fat and muscle. AA + C increased body fat without further alteration in muscle mass. Changes in BMI did not reflect changes in body composition. Sarcopenia at baseline was a negative prognostic factor in this population.