Targeting DNA repair with combination veliparib (ABT-888) and temozolomide in patients with metastatic castration-resistant prostate cancer
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Androgen receptor-mediated transcription is directly coupled with the induction of DNA damage, and castration-resistant tumor cells exhibit increased activity of poly (ADP-ribose) polymerase (PARP)-1, a DNA repair enzyme. This study assessed the efficacy and safety of low dose oral PARP inhibitor veliparib (ABT-888) and temozolomide (TMZ) in docetaxel-pretreated patients with metastatic castration-resistant prostate cancer (mCRPC) in a single-arm, open-label, pilot study. Patients with mCRPC progressing on at least one docetaxel-based therapy and prostate specific antigen (PSA) ≥ 2 ng/mL were treated with veliparib 40 mg twice daily on days 1–7 and TMZ once daily (150 mg/m2/day cycle 1; if well tolerated then 200 mg/m2/day cycle 2 onwards) on days 1–5 q28 days. Patients received 2 (median) treatment cycles (range, 1–9). The primary endpoint was confirmed PSA response rate (decline ≥ 30 %). Twenty-six eligible patients were enrolled, 25 evaluable for PSA response. Median baseline PSA was 170 ng/mL. Two patients had a confirmed PSA response (8.0 %; 95 % CI: 1.0–26.0), 13 stable PSA, and 10 PSA progression. The median progression-free survival was 9 weeks (95 % CI: 7.9–17) and median overall survival 39.6 weeks (95 % CI: 26.6–not estimable). The most frequent treatment-emergent adverse events (AEs) were thrombocytopenia (77 %), anemia (69 %), fatigue (50 %), neutropenia (42 %), nausea (38 %), and constipation (23 %). Grade 3/4 AEs occurring in > 10 % of patients were thrombocytopenia (23 %) and anemia (15 %). Veliparib and TMZ combination was well tolerated but with modest activity. Biomarker analysis supported the proof of concept that this combination has some antitumor activity in mCRPC.
KeywordsPilot study Metastatic castration-resistant prostate cancer Veliparib Temozolomide Combination therapy
Statistical analyses were performed by Matt Dudley, PhD and medical writing assistance by Keith J. Gaddie, PhD of AbbVie. Medical writing assistance was provided by Mukund Nori, PhD, MBA, CMPP and Helen Varley, PhD, CMPP of UBC-Envision Group; financial support for this service was provided by AbbVie.
AbbVie provided financial support for the study and participated in the design, study conduct, analysis and interpretation of data as well as the writing, review and approval of the manuscript.
Conflict of interest
Jiang Qian, Evelyn McKeegan, Marion Refici-Buhr, Brenda Chyla. Stacie Shepherd and Vincent Giranda are employees and stock owners of AbbVie. Maha Hussain, Michael Carducci, Susan Slovin, Jeremy Cetnar, and Joshi Alumkal have no conflicts to disclose.
Trial registration ID: NCT01085422.
This study was sponsored by AbbVie Inc. The institutions of authors Maha Hussain, Michael Carducci, Susan Slovin, Jeremy Cetnar, and Joshi Alumkal received funding support from AbbVie to conduct this study. This trial was conducted by the Prostate Cancer Clinical Trials Consortium (PCCTC), a program of the Prostate Cancer Foundation and the Department of Defense Prostate Cancer Research Program (PCRP).
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