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

BACKGROUND: Mutations in the androgen receptor (AR) ligand-binding domain (LBD), such as F877L and T878A, have been associated with resistance to next-generation AR-directed therapies. ARN-509-001 was a phase I/II study that evaluated apalutamide activity in castration-resistant prostate cancer (CRPC). Here, we evaluated the type and frequency of 11 relevant AR-LBD mutations in apalutamide-treated CRPC patients. PATIENTS AND METHODS: Blood samples from men with nonmetastatic CRPC (nmCRPC) and metastatic CRPC (mCRPC) pre- or post-abiraterone acetate and prednisone (AAP) treatment (≥6 months' exposure) were evaluated at baseline and disease progression in trial ARN-509-001. Mutations were detected in circulating tumor DNA using a digital polymerase chain reaction-based method known as BEAMing (beads, emulsification, amplification and magnetics) (Sysmex Inostics' GmbH). RESULTS: Of the 97 total patients, 51 had nmCRPC, 25 had AAP-naïve mCRPC, and 21 had post-AAP mCRPC. Ninety-three were assessable for the mutation analysis at baseline and 82 of the 93 at progression. The overall frequency of detected AR mutations at baseline was 7/93 (7.5%) and at progression was 6/82 (7.3%). Three of the 82 (3.7%) mCRPC patients (2 AAP-naïve and 1 post-AAP) acquired AR F877L during apalutamide treatment. At baseline, 3 of the 93 (3.2%) post-AAP patients had detectable AR T878A, which was lost after apalutamide treatment in 1 patient who continued apalutamide treatment for 12 months. CONCLUSIONS: The overall frequency of detected mutations at baseline (7.5%) and progression (7.3%) using the sensitive BEAMing assay was low, suggesting that, based on this assay, AR-LBD mutations such as F877L and T878A are not common contributors to de novo or acquired resistance to apalutamide. CLINICALTRIALS.GOV IDENTIFIER: NCT01171898.

Sunitinib in combination with docetaxel and prednisone in chemotherapy-naive patients with metastatic, castration-resistant prostate cancer: a phase 1/2 clinical trial.

BACKGROUND: This phase 1/2 study assessed sunitinib combined with docetaxel (Taxotere) and prednisone in chemotherapy-naive metastatic, castration-resistant prostate cancer (mCRPC) patients. PATIENTS AND METHODS: To determine the recommended phase 2 dose (RP2D), 25 patients in four dose escalation cohorts received 3-week cycles of sunitinib (2 weeks on, 1 week off), docetaxel and prednisone, preceded by a 4-week sunitinib 50 mg/day lead in. RP2D was evaluated in 55 additional patients. The primary end point was prostate-specific antigen (PSA) response rate. RESULTS: One phase 1 dose-limiting toxicity occurred (grade 3 hyponatremia). The RP2D was sunitinib 37.5 mg/day, docetaxel 75 mg/m(2) and prednisone 5 mg b.i.d. During phase 2, confirmed PSA responses occurred in 31 patients [56.4% (95% confidence interval 42.3-69.7)]. Median time to PSA progression was 9.8 months. Forty-one patients (75%) were treated >3 months, 12 (22%) completed the study (16 cycles) and 43 (78%) discontinued (36% for disease progression and 27% adverse events). The most frequent treatment-related grade 3/4 adverse events were neutropenia (53%; 15% febrile) and fatigue/asthenia (16%). Among 33 assessable patients, 14 (42.4%) had confirmed partial response. Median progression-free and overall survivals were 12.6 and 21.7 months, respectively. CONCLUSION: This combination was moderately well tolerated, with promising response rate and survival benefit, justifying further investigation in mCRPC.

A phase I study of sunitinib combined with modified FOLFOX6 in patients with advanced solid tumors.

PURPOSE: This phase I study assessed the safety, tolerability, maximum tolerated dose (MTD), pharmacokinetics, and preliminary antitumor effects of sunitinib combined with modified FOLFOX6 (mFOLFOX6). METHODS: Patients with advanced solid malignancies received mFOLFOX6 in 2-week cycles with escalating sunitinib doses (25, 37.5, and 50 mg/day) on three schedules: 2 weeks on, 2 weeks off (2/2); 4 weeks on, 2 weeks off (4/2); or continuous daily dosing (CDD). Patients received up to 8 treatment cycles (Schedule 2/2 and CDD schedule) or 6 cycles (Schedule 4/2). An expansion cohort enrolled patients with metastatic colorectal cancer at the Schedule 2/2 MTD. RESULTS: Overall, 53 patients were enrolled, with 43 evaluable for dose-limiting toxicity (DLT). On Schedule 2/2 (n = 18), DLTs occurred in three patients at 50 mg/day (grade 4 neutropenia [n = 1]; grades 3 and 4 thrombocytopenia [n = 2]) and two patients achieved partial responses (PRs). On Schedule 4/2 (n = 13), 37.5 mg/day exceeded the MTD with two DLTs (febrile neutropenia and grade 4 hypokalemia, respectively). On the CDD schedule (n = 12), the MTD was 25 mg/day; one DLT (grade 3 stomatitis) was reported and two patients achieved PRs. The most common adverse events were neutropenia, fatigue, and thrombocytopenia. No clinically significant drug-drug interactions were apparent between sunitinib, its metabolite SU12662, and mFOLFOX6. CONCLUSIONS: Sunitinib combined with mFOLFOX6 had acceptable tolerability. The MTDs were sunitinib 50 mg/day on Schedule 2/2 and 25 mg/day on the CDD schedule. A MTD for Schedule 4/2 was not established.