A phase II trial of abiraterone acetate (AA) without prednisone in castration resistant prostate cancer (CRPC).

2017 ◽  
Vol 35 (15_suppl) ◽  
pp. 5040-5040
Author(s):  
Rana R. McKay ◽  
Lillian Werner ◽  
Alexandra Jones ◽  
Atish Dipankar Choudhury ◽  
Mark Pomerantz ◽  
...  
Keyword(s):  
Phase Ii ◽  
Abiraterone Acetate ◽  
Primary Objective ◽  
Castration Resistant Prostate Cancer ◽  
Adrenal Androgens ◽  
Castration Resistant ◽  
Mineralocorticoid Antagonist ◽  
Psa Progression ◽  
Clinically Significant ◽  
Clinical Trial Information

5040 Background: AA blocks CYP17 and suppresses adrenal androgens and glucocorticoids. Given the risk of mineralocorticoid excess (ME), AA is administered with corticosteroids. In this phase II multicenter, single-arm study, we assess the safety of AA without steroids in CRPC. The primary objective is to determine the proportion of men requiring prednisone to manage ME. Methods: Eligible patients had CRPC with controlled blood pressure (BP) ( < 140/90 on ≤3 agents) and a normal or ≥3.5 mmol/L potassium. Patients initially received AA (1000 mg daily) alone. Patients who developed a BP ≥ 140/90 were treated with anti-hypertensives (HTN) and/or a mineralocorticoid antagonist (MA) prior to steroids. Hypokalemia was treated with supplementation or a MA. Patients with persistent or severe ME were initiated on prednisone (5 mg twice daily). To assess response to steroids, prednisone was added to AA at PSA progression. Therapy was continued until radiographic progression, toxicity, or withdrawal. Results: 60 patients were enrolled of whom 51 (83%) had metastases 16 (27%) received prior chemotherapy, 6 (10%) enzalutamide, and 4 (7%) ketoconazole. Grade (G) 3-4 adverse events (AEs) of interest included HTN (G3 n = 8, 13%; G4 n = 1, 2%), hypokalemia (G3 n = 4, 7%; G4 n = 0), fatigue (G3 n = 1, 2%; G4 n = 0). There was no G ≥3 edema. 9 patients (15%) initiated prednisone for toxicity: HTN (n = 3, 5%), hypokalemia (n = 4, 7%), fatigue (n = 2, 3%). Baseline PSA was 15.4 ng/mL. Time to nadir PSA was 2.5 months (IQR 1.4, 6.3) and median nadir PSA was 2.1 ng/mL. 67% of patients (n = 40) experienced a ≥50% PSA decline and 35% (n = 21) experienced a ≥90% decline. 19 patients (32%) initiated prednisone for PSA progression. Median time to prednisone initiation in patients with PSA progression was 6.1 months (IQR 4.9, 11.7); 5 patients (8.3%) had a PSA decline and 1 achieved a ≥50% decline. Levels of corticosteroids will be reported. Conclusions: In CRPC, AA without steroids is feasible, however clinically significant AEs, particularly HTN, can occur in a minority of patients. HTN and hypokalemia can be treated with anti-HTN agents or potassium without steroids in the majority. Use of AA without prednisone needs to be balanced with the potential risk of toxicity. Clinical trial information: NCT02025010.

Evaluating the safety of abiraterone acetate (AA) and docetaxel (D) administered in combination in patients (Pts) with metastatic castration-resistant prostate cancer (mCRPC).

2014 ◽  
Vol 32 (4_suppl) ◽  
pp. 205-205 ◽  
Author(s):  
Scott T. Tagawa ◽  
David M. Nanus ◽  
Edwin M. Posadas ◽  
Daniel Peter Petrylak ◽  
Justine Yang Bruce ◽  
...  
Keyword(s):  
Specific Antigen ◽  
Systemic Exposure ◽  
Abiraterone Acetate ◽  
Maximum Plasma ◽  
Castration Resistant Prostate Cancer ◽  
Time Curve ◽  
Castration Resistant ◽  
Psa Progression ◽  
Dose Limiting Toxicity ◽  
Clinical Trial Information

205 Background: D and AA may have complementary mechanisms of action; coadministration may be beneficial. A phase Ib study assesses the safety of escalating doses of D + AA. Methods: Up to4 cohorts (C) of chemo-naïve mCRPC pts would receive D + AA. Data for C1 and C2 are presented. Primary end point: proportion of pts with dose-limiting toxicity (DLT) between Wks 2 and 7, defined as grade (Gr) ≥ 3 non-heme toxicity, Gr 4 neutropenia (absolute neutrophil count < 500/mm3) > 7 days (or febrile neutropenia), Gr 4 thrombocytopenia, or other intolerable toxicity. D + AA was deemed safe if ≤ 33% of pts experienced DLT. Pharmacokinetic (PK) parameters were evaluated for D and AA alone and in combination. Results: 15 pts were treated and 6 pts/C were evaluable for DLT assessment. 2 DLTs were observed in C1, and 1 in C2. 73% and 87% of pts had confirmed ≥ 90% and ≥ 50% prostate-specific antigen (PSA) decline, respectively. Median time to PSA progression has not yet been reached. Systemic exposure, based on maximum plasma concentration (Cmax) and area under the concentration–time curve [(AUC)∞ for D, AUC24 for abiraterone (ABI)], was comparable for both D and AA alone and for D + AA. 3 pts in C3 (D 75 mg/m2+ AA 1000 mg) have been treated past Wk 7 without DLT. Conclusions: D + AA was well tolerated in the cohorts tested. Preliminary results justify further evaluation of safety and efficacy in additional Cs. Clinical trial information: NCT01400555. [Table: see text]

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

2020 ◽  
Vol 38 (15_suppl) ◽  
pp. TPS5591-TPS5591
Author(s):  
Matthew Raymond Smith ◽  
Neeraj Agarwal ◽  
Tilman Todenhöfer ◽  
Redas Trepiakas ◽  
Jae-Lyun Lee ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Cell Cycle ◽  
Phase Ii ◽  
Objective Response ◽  
Metastatic Breast ◽  
Abiraterone Acetate ◽  
Controlled Study ◽  
Castration Resistant Prostate Cancer ◽  
Castration Resistant ◽  
Psa Progression

TPS5591 Background: Despite recent advances, nearly all patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) experience disease progression and cancer-specific mortality. Persistent or reactivated androgen receptor (AR) signaling and/or activation of pathways in cross-talk with AR signaling are key drivers of mCRPC progression. Evidence suggests that AR signaling promotes translation of D-type cyclins resulting in cyclin-dependent kinase 4 and 6 (CDK4&6) activation and cell cycle progression. Abemaciclib is an oral selective inhibitor of CDK4&6 dosed on a continuous schedule, that is FDA-approved in combination with endocrine therapy or as monotherapy to treat HR+, HER2- metastatic breast cancer pts. Preclinical studies with prostate cancer cell lines and xenograft models showed that abemaciclib induces cell cycle arrest and tumor growth inhibition. The hypothesis is that addition of abemaciclib to AR targeted therapy may be an effective treatment for mCRPC pts. Methods: CYCLONE 2 (NCT03706365) is a phase II, randomized, double-blind, multicenter, placebo-controlled study to assess the safety and efficacy of abemaciclib in combination with abiraterone acetate plus prednisone (AA+P) as first-line treatment of pts with mCRPC. The study is designed in two parts. Part 1 is a 30-patient safety lead-in to determine the recommended phase II dose (RP2D; 150 mg or 200 mg, twice daily) of abemaciclib in combination with AA (1000 mg, once daily) + P (5 mg, twice daily). In part 2, 150 pts are randomized 1:1 to abemaciclib at the RP2D with AA+P or placebo with AA+P. Pts who received prior AA+P, enzalutamide, apalutamide, darolutamide, radiopharmaceuticals, or sipuleucel-T are excluded. Prior docetaxel for metastatic hormone-sensitive prostate cancer, but not for mCRPC, is allowed. Pts must have progressive mCRPC (by PSA and/or imaging) and an accessible metastatic lesion for tumor biopsy. The co-primary objectives are radiographic PFS (per RECIST1.1 for soft tissue and PCWG3 for bone) and time to PSA progression. Secondary objectives include safety, objective response rate, duration of response, OS, time to symptomatic progression, and pharmacokinetics. Assuming hazard ratios of 0.64 (rPFS) and 0.6 (PSA progression), the study is powered to 80% and 85%, respectively, to test the superiority of abemaciclib plus AA+P vs. placebo plus AA+P at one-sided α=0.1 using stratified log-rank tests. Part 1 is completed and part 2 is enrolling in 70 sites worldwide. Clinical trial information: NCT03706365 .

scholarly journals Significant and Sustained Antitumor Activity in Post-Docetaxel, Castration-Resistant Prostate Cancer With the CYP17 Inhibitor Abiraterone Acetate

2010 ◽  
Vol 28 (9) ◽  
pp. 1489-1495 ◽  
Author(s):  
Alison H.M. Reid ◽  
Gerhardt Attard ◽  
Daniel C. Danila ◽  
Nikhil Babu Oommen ◽  
David Olmos ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Antitumor Activity ◽  
Phase Ii ◽  
Specific Antigen ◽  
Abiraterone Acetate ◽  
Phase Iii ◽  
Castration Resistant Prostate Cancer ◽  
End Point ◽  
Castration Resistant ◽  
Psa Progression

Purpose The principal objective of this trial was to evaluate the antitumor activity of abiraterone acetate, an oral, specific, irreversible inhibitor of CYP17 in docetaxel-treated patients with castration-resistant prostate cancer (CRPC). Patients and Methods In this multicenter, two-stage, phase II study, abiraterone acetate 1,000 mg was administered once daily continuously. The primary end point was achievement of a prostate-specific antigen (PSA) decline of ≥ 50% in at least seven of 35 patients. Per an attained phase II design, more than 35 patients could be enrolled if the primary end point was met. Secondary objectives included: PSA declines of ≥ 30% and ≥ 90%; rate of RECIST (Response Evaluation Criteria in Solid Tumors) responses and duration on study; time to PSA progression; safety and tolerability; and circulating tumor cell (CTC) enumeration. Results Docetaxel-treated patients with CRPC (N = 47) were enrolled. PSA declines of ≥ 30%, ≥ 50% and ≥ 90% were seen in 68% (32 of 47), 51% (24 of 47), and 15% (seven of 47) of patients, respectively. Partial responses (by RECIST) were reported in eight (27%) of 30 patients with measurable disease. Median time to PSA progression was 169 days (95% CI, 113 to 281 days). The median number of weeks on study was 24, and 12 (25.5%) of 47 patients remained on study ≥ 48 weeks. CTCs were enumerated in 34 patients; 27 (79%) of 34 patients had at least five CTCs at baseline. Eleven (41%) of 27 patients had a decline from at least five to less than 5 CTCs, and 18 (67%) of 27 had a ≥ 30% decline in CTCs after starting treatment with abiraterone acetate. Abiraterone acetate was well tolerated. Conclusion Abiraterone acetate has significant antitumor activity in post-docetaxel patients with CRPC. Randomized, phase III trials of abiraterone acetate are underway to define the future role of this agent.

KEYNOTE-199 cohorts (C) 4 and 5: Phase II study of pembrolizumab (pembro) plus enzalutamide (enza) for enza-resistant metastatic castration-resistant prostate cancer (mCRPC).

2020 ◽  
Vol 38 (15_suppl) ◽  
pp. 5543-5543 ◽  
Author(s):  
Christopher J. Hoimes ◽  
Julie N Graff ◽  
Scott T. Tagawa ◽  
Clara Hwang ◽  
Deepak Kilari ◽  
...  
Keyword(s):  
Phase Ii ◽  
Phase Ii Study ◽  
Phase Iii ◽  
Castration Resistant Prostate Cancer ◽  
Fisher Syndrome ◽  
Castration Resistant ◽  
Psa Progression ◽  
Grade 3 ◽  
Ongoing Phase ◽  
Clinical Trial Information

5543 Background: Initial evidence suggests activity of pembro + enza in patients (pts) resistant to enza. We present results from the multicohort phase II study KEYNOTE-199 (NCT02787005) in chemotherapy-naive pts with mCRPC treated with pembro + enza after progression with enza and who had RECIST-measurable (C4) or bone-predominant (C5) disease. Methods: Pts who did or did previously receive abiraterone and for whom enza treatment failed after clinically meaningful response received pembro 200 mg Q3W, with continuation of enza for up to 2 y or until progression, toxicity, or withdrawal. End point was ORR per RECIST v1.1 (C4) by blinded independent central review (primary); DOR (C4), time to PSA progression, rPFS, OS, and safety. Results: A total of126 pts (C4, 81; C5, 45) were treated. Median (range) PSA was 31 ng/mL (0.4-1667) in C4 and 19 ng/mL (1-1750) in C5.Median (range) time from enrollment to data cut off was 15 mo (7-21) in C4 and 19 mo (7-21) in C5. In C4, ORR (95% CI) was 12% (6-22; 2 CRs, 8 PRs) and median (range) DOR was 6 mo (3+ to 13); 60% of pts had DOR ≥6 mo. DCR (CR + PR + SD) was 51% in C4 and C5. Median (95% CI) time to PSA progression was 4 mo (4-4) in C4 and 4 mo (4-4) in C5. Median (95% CI) rPFS was 4 mo (3-6) for C4 and 4 mo (3-6) for C5; 12-mo rPFS rate was 17% in C4 and 23% in C5. Median (95% CI) OS was NR (16-NR) in C4 and 19 (14-NR) mo in C5; 12-mo OS rate was 70% in C4 and 75% in C5. Shorter median OS was more associated with prior enza treatment <6 mo than with prior enza treatment ≥6 mo. Liver metastasis was associated with shorter median OS however, median OS in visceral disease subgroups appeared longer than expected. Any-grade/grade ≥3 treatment-related AEs occurred in 75%/26% of pts in C4 and 69%/24% in C5. Two pts in C5 died of immune-related AEs (Miller Fisher syndrome and myasthenia gravis). Any-grade/grade 3/4 rash (regardless of relatedness) was higher than that in prior reports for individual agents (33%/6%). Conclusions: Pembro + enza after enza resistance had manageable safety and showed antitumor activity for RECIST-measurable and bone-predominant mCRPC. This combination is being evaluated in an ongoing phase III combination trial. Clinical trial information: NCT02787005 . [Table: see text]

scholarly journals A prognostic model for stratifying clinical outcomes in chemotherapy-naive metastatic castration-resistant prostate cancer patients treated with abiraterone acetate

2017 ◽  
Vol 12 (2) ◽  
pp. E47-52 ◽  
Author(s):  
Daniel Joseph Khalaf ◽  
Claudia M. Avilés ◽  
Arun A. Azad ◽  
Katherine Sunderland ◽  
Tilman Todenhöfer ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Clinical Outcomes ◽  
Group Performance ◽  
Eastern Cooperative Oncology Group ◽  
Specific Antigen ◽  
Prognostic Index ◽  
Abiraterone Acetate ◽  
Castration Resistant Prostate Cancer ◽  
Castration Resistant ◽  
Psa Progression

Introduction: Recently, a prognostic index including six risk factors (RFs) (unfavourable Eastern Cooperative Oncology Group performance status [ECOG PS], presence of liver metastases, short response to luteinizing hormone-releasing hormone [LHRH] agonists/ antagonists, low albumin, increased alkaline phosphatase [ALP] and lactate dehydrogenase [LDH]) was developed from the COUAA- 301 trial in post-chemotherapy metastatic castration-resistant prostate cancer (mCRPC) patients treated with abiraterone acetate. Our primary objective was to evaluate this model in a cohort of chemotherapy-naive mCRPC patients receiving abiraterone.Methods: We identified 197 chemotherapy-naive patients who received abiraterone at six BC Cancer Agency centres and who had complete information on all six RFs. Study endpoints were prostate-specific antigen (PSA) response rate (RR), time to PSA progression, time on treatment, and overall survival (OS). PSA RR and survival outcomes were compared using Χ2 test and log-rank test. Multivariable Cox proportional hazard analysis was performed to identify RFs independently associated with OS.Results: Patients were classified into good (0‒1 RFs), intermediate (2‒3 RFs), and poor (4‒6 RFs) prognostic groups (33%, 52%, and 15%, respectively). For good-, intermediate-, and poor-risk patients, PSA RR (≥50% decline) was 60% vs. 42% vs. 40% (p=0.05); median time to PSA progression was 7.3 vs. 5.3 vs. 5.0 months (p=0.02); and median OS was 29.4 vs. 13.8 vs. 8.7 months (p<0.0001).Conclusions: The six-factor prognostic index model stratifies clinical outcomes in chemotherapy-naive mCRPC patients treated with abiraterone. Identifying patients at risk of poor outcome is important for informing clinical practice and clinical trial design.

Phase II multicenter study of abiraterone acetate (AA) plus prednisone therapy in docetaxel-treated castration-resistant prostate cancer (CRPC) patients (pts): Impact of prior ketoconazole (keto)

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. 5048-5048 ◽  
Author(s):  
D. C. Danila ◽  
J. de Bono ◽  
C. J. Ryan ◽  
S. Denmeade ◽  
M. Smith ◽  
...  
Keyword(s):  
Abiraterone Acetate ◽  
Phase Iii ◽  
Castration Resistant Prostate Cancer ◽  
Castration Resistant ◽  
Pivotal Study ◽  
Heavily Pretreated ◽  
Psa Progression ◽  
Hormonal Therapies ◽  
Ecog Ps ◽  
Anti Tumor Activity

5048 Background: AA is a potent blocker of CYP17, required for synthesis of testosterone in the testes, adrenals, and prostate tissue. Study objectives included confirming AA antitumor activity and safety in multicenter setting, describing changes in ECOG PS, and comparing keto-naïve pts to keto-exposed pts. Methods: The 58 pts had progressive, metastatic CRPC and had failed hormonal therapy and up to two cytotoxic regimens, including docetaxel. AA (1,000 mg QD) and prednisone (5mg BID) were administered daily, the registration trial regimen. 56/58 pts had available data. Results: Baseline demographics: median age - 69.0 (44–86) yrs; median PSA - 151.00 (10.0–3846.0) ng/mL; ECOG 0 (n = 23), 1 (n = 30), 2 (n = 2), missing (n = 1); median prior hormonal therapies were 4 and chemo 1; 24 pts had prior keto, 32 pts were keto-naïve and 2 pts had no data on keto exposure. 45% pts had total maximal PSA decline ≥50%. Total maximal PSA decline (≥30%, ≥50% and ≥90%) in prior keto vs. keto-naïve pts was observed respectively, in: 10 (42%) vs. 20 (63%) pts; 8 (33%) vs. 17 (53%); 1 (4%) vs. 10 (31%). From 32 pts with ECOG 1 or 2, 16 pts (50%, 95% CI 32–68) improved (PS 1 to 0 in 14 pts, PS 2 to 1 in 1 pt; PS 2 to 0 in 1 pt); 39 pts (64% of total 58 pts) maintained PS. Median time to PSA progression was 169 days (95% CI 82–200): keto-naïve-198 days, prior keto-99 days. The majority of AA-related adverse events (AEs) were grade 1–2. No AA-related grade 4 AE was noted. Conclusions: Abiraterone acetate was well-tolerated and produced anti-tumor activity in heavily pretreated pts, as evidenced by PSA declines and improved PS. Incidence of mineralocorticoid-related AEs (HTN or hypokalemia) was reduced with the addition of low-dose prednisone. The keto-naïve post-docetaxel CRPC population was selected for the ongoing phase III pivotal study to confirm these results. [Table: see text]

Efficacy of abiraterone acetate in the treatment of castration-resistant prostate cancer: Early results from the German compassionate-use program.

2012 ◽  
Vol 30 (15_suppl) ◽  
pp. e15195-e15195
Author(s):  
Carsten Henning Ohlmann ◽  
Michael Stöckle ◽  
David A. Pfister ◽  
Axel Heidenreich ◽  
Axel S. Merseburger ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Overall Survival ◽  
Disease Progression ◽  
Objective Response ◽  
Abiraterone Acetate ◽  
Castration Resistant Prostate Cancer ◽  
Compassionate Use ◽  
Castration Resistant ◽  
Psa Progression

e15195 Background: Abiraterone acetate (AA) plus prednisone (P) has demonstrated an improved survival of patients with castration-resistant prostate cancer (CRPC) compared to placebo plus P in a large phase III trial. In Germany, patients were able to receive AA within a compassionate-use program (CUP). Here, we report the first results of the program. Methods: Patients were eligible for the CUP if they progressed on or after at least one cytotoxic chemotherapy regimens. For CUP entry, patients were considered to have disease progression if they had radiographic evidence of disease progression in soft tissue or bone with or without PSA-progression and ongoing androgen deprivation. Patients received AA 1000mg daily plus prednisone 5mg BID until progression of disease or unacceptable toxicity. Results: Between 02-05/2011, 398 patients were registered for the CUP in Germany. Data from 191/350 (47.9%) of the patients treated at 10 different sites were available for evaluation of efficacy. Median age was 70.72yrs (52.35-87.61) and patients received a median of 1 (1-4) chemotherapy lines prior to CUP entry. Median PSA at baseline was 220.5 ng/ml (0.47-4245); 168 (88%) of patients presented with bone metastasis. With regard to efficacy, 64/191 (33.5%) of the patients showed an unconfirmed PSA-response ≥50%. At a median follow-up of 5.3 months, 51/191 (26.7%) patients had died, resulting in a median PSA-progression free and overall survival of 8.3 and 10.61 months, respectively. In a subset of patients (71/191, 37.2%) data regarding objective response was available with 25/71 (35.2%) achieving an objective response. Data from 114 pts. revealed fatigue (20.3%), hot flushes (15.8%), edema (10.6%), elevated liver enzymes (8.0%) and asthenia (7.9%) being the most frequent toxicities (any grade). Conclusions: Treatment of CRPC patients with AA outside controlled clinical trials leads to considerable PSA- and objective response rates with a favourable toxicity profile, comparable to the results from COU-AA-301 registration trial. Due to the short median follow-up, conclusions regarding PSA-progression free and overall survival may not be drawn.

Pilot study of veliparib (ABT-888) with temozolomide (TMZ) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC).

2012 ◽  
Vol 30 (5_suppl) ◽  
pp. 224-224 ◽  
Author(s):  
Maha Hussain ◽  
Michael Anthony Carducci ◽  
Susan F. Slovin ◽  
Jeremy Paul Cetnar ◽  
Jiang Qian ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Type I Error ◽  
Objective Response ◽  
Progression Free Survival ◽  
Primary Objective ◽  
Type I ◽  
Castration Resistant Prostate Cancer ◽  
Castration Resistant ◽  
Psa Response ◽  
Clinically Significant

224 Background: Castration-resistant PC tumors exhibit increased PARP activity (critical enzymes for DNA damage repair). Veliparib is a novel, oral, potent inhibitor of PARP-1 and PARP-2. Preclinically, resistance to oral TMZ treatment in the PC3-Luc prostate cancer mouse model was reversed when mice were treated with veliparib. Based on the synergistic interaction, we evaluated the efficacy and safety of veliparib + TMZ in mCRPC pts. Methods: Eligible pts had mCRPC, PSA>2 ng/mL, progressed on at least one docetaxel based therapy and adequate organ function. Pts received veliparib 40 mg BID Days (D) 1-7 and TMZ D1-5 in 28D cycle (C) until disease progression (PD) or unacceptable toxicities. Tumor response was assessed every 8 weeks. Primary objective: Efficacy based on rate of PSA decline of 30% or greater. Secondary objectives: safety, RECIST objective response rate, progression-free survival (PFS), overall survival (OS) and biomarker analyses. A sample size of 25 pts provided 76% power to differentiate between PSA response rates of 5 and 20% at 1-sided type I error rate of 0.1. Results: 26 pts were enrolled; median age 67 years [55, 81]; median baseline PSA 107 ng/ml (6.9, 4584.4); 7/26 (27%) had 2 prior therapies. Median Cs of veliparib + TMZ received were 2 (range 1–9). Most frequent treatment related adverse events (AE) were fatigue (50%), nausea (38%) and constipation (23%). Grade 3/4 AEs in >10% of pts was thrombocytopenia (15%). All pts are off therapy. 25 pts were PSA response evaluable; 2 pts had a confirmed PSA response; 1 pt had a 37% decrease in PSA while the other pt had a 96% decrease in PSA and a 40% reduction in tumor size. 4/25 pts had stable disease for a minimum of 4 months (m). Median PFS was 2.1 m [95% CI: 1.8, 3.9]; 11/26 pts have died with median OS of 9.1 m [95% CI: 5.5, 11.7]. There was a negative correlation between change from baseline in circulating tumor cells and PFS. Conclusions: Veliparib + TMZ were well tolerated with evidence of some activity. Due to lack of activity of TMZ in CRPC,veliparib-induced potentiation of TMZ may not be clinically significant. Other combinations will be explored with higher doses of veliparib. Biomarker data will be presented.

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