Brian A. Wood

Double-Blind, Placebo-Controlled, Randomized Phase 2 Study of the Proapoptotic Agent AT-101 Plus Docetaxel, in Second-Line Non-small Cell Lung Cancer

Background: AT-101 is an inhibitor of Bcl-2 family proteins including Bcl-2, Bcl-xL, Mcl-1, and Bcl-w. In vivo and in vitro studies have exhibited broad activity of AT-101, including synergy with docetaxel in non-small cell lung cancer tumor models. Methods: We conducted a prospective, randomized (1:1), double-blind, placebo-controlled phase 2 study. Eligible patients must have received one prior chemotherapeutic regimen for advanced or metastatic non-small cell lung cancer and may also have received therapy with an epidermal growth factor receptor inhibitor. Patients received AT-101 (40 mg b.i.d. × 3 days) or placebo in combination with docetaxel (75 mg/m2 on day 1) every 21 days. The primary endpoint was progression-free survival (PFS) as determined by independent review; other endpoints include overall survival and PFS by investigator determination. Approximately 102 patients were planned to provide 70 events (80% power, hazard ratio [HR] of 0.6, one-sided alpha of 0.1). Results: One hundred six patients were assigned to treatment and 105 patients received at least one dose of AT-101 or placebo. Baseline factors were balanced between treatment groups: median age 59 years; 77% men, and 79% current or former smokers. Ninety-three percent of patients had distant metastatic disease at randomization and 56% squamous histology. The most frequently reported adverse events were fatigue (18%), anemia (18%), and dyspnea (18%). No statistically significant differences in serious adverse events were observed between AT-101 and placebo; grade 1/2 headaches appeared more frequently with AT-101 (9% versus 0%) and neutropenia was reported more frequently in the docetaxel plus placebo arm compared with docetaxel plus AT-101 (17% versus 8%). Unlike trials with continuous daily dosing of AT-101, no cases of small bowel obstruction were reported. The response rate and median PFS were not different between the arms by independent review, PFS 7.5 weeks for docetaxel plus AT-101 and 7.1 weeks for docetaxel plus placebo arms (HR, 1.04; p = 0.57). The median overall survival was 7.8 months for docetaxel plus AT-101 versus 5.9 months for docetaxel plus placebo (HR, 0.82; p = 0.21). Conclusions: The primary endpoint of improved PFS for AT-101 plus docetaxel was not met. AT-101 plus docetaxel was well tolerated with an adverse event profile indistinguishable from the base docetaxel regimen. AT-101 is the first oral, pan Bcl-2 family inhibitor to exhibit a possible survival benefit in a randomized study.

Evaluating the Value of Number of Cycles of Docetaxel and Prednisone in Men With Metastatic Castration-Resistant Prostate Cancer

BACKGROUND The optimal number of 3-wk docetaxel plus prednisone (DP) cycles for metastatic castration-resistant prostate cancer (mCRPC) is unclear. OBJECTIVE A retrospective analysis of two clinical trials was performed to evaluate the association of the number of cycles with overall survival (OS). DESIGN, SETTING, AND PARTICIPANTS An exploratory analysis compared outcomes of 332 men who received DP in the TAX-327 trial, which stipulated up to 10 cycles, and 220 men who received DP in CS-205, a randomized phase 2 trial comparing DP plus AT-101 (bcl-2 inhibitor) versus DP plus placebo, which allowed up to 17 cycles. MEASUREMENTS Patients who completed 10 cycles of DP without progression in both trials were included. Men in both arms of CS-205 were combined for analysis, as no significant differences in outcomes were observed. OS was estimated from the date of cycle 10 docetaxel infusion. RESULTS AND LIMITATIONS The number of men receiving 10 cycles was similar (p=0.26) in the two trials (166 [50.0%] in TAX-327 vs 99 [45.0%] in CS-205; the latter group received a median of five additional cycles). Six- and 12-mo estimated survival after cycle 10 was 92.2% (95% confidence interval [CI], 86.9-95.4%) and 74.6% (CI, 67.2-80.5%) in TAX-327, compared with 92.8% (CI, 85.5-96.5) and 63.4% (CI, 51.8-72.9%) in CS-205. Subanalyses suggested that <10 cycles may have a negative impact and prostate-specific antigen (PSA) declines at cycle 10 may carry a favorable impact. The significance of continued PSA declines up to 17 cycles is unclear. Limitations of a retrospective analysis apply. CONCLUSIONS A survival benefit was not detected with >10 cycles of DP in men with mCRPC in this retrospective hypothesis-generating analysis.

Ability of C-reactive protein to complement multiple prognostic classifiers in men with metastatic castration resistant prostate cancer receiving docetaxel-based chemotherapy.

Study Type – Retrospective analysis of clinical trial

Radiographic progression by Prostate Cancer Working Group (PCWG)‐2 criteria as an intermediate endpoint for drug development in metastatic castration‐resistant prostate cancer

To investigate the association of radiographic progression defined by Prostate Cancer Working Group (PCWG)‐2 guidelines and overall survival (OS) in men with metastatic castration‐resistant prostate cancer (mCRPC).

Neutropenia as a Potential Pharmacodynamic Marker for Docetaxel-Based Chemotherapy in Men With Metastatic Castration-Resistant Prostate Cancer

BACKGROUND Docetaxel clearance appears increased in men who are castrated. Neutropenia in cycle 1 may be a pharmacodynamic marker for docetaxel, which may enable tailored dosing in metastatic castration-resistant prostate cancer (mCRPC). PATIENTS AND METHODS The association of cycle 1 neutropenia with overall survival (OS) was examined post hoc in a randomized phase II trial of 221 men with mCRPC who received docetaxel-prednisone combined with placebo or AT-101 (bcl-2 inhibitor); weekly blood cell counts were performed during the first cycle. Patients from both arms were combined because no outcome and toxicity differences were observed. OS was calculated from randomization by the Kaplan-Meier method, and Cox proportional hazards regression models were used to estimate the association with OS. RESULTS The difference in OS between men with day 8 ≥grade 3 neutropenia and those with ≤grade 2 neutropenia was significant after adjusting for trial stratification factors, pain, and performance status (hazard ratio [HR] 0.64; 2P = .048). Results were similar for logarithmic neutrophil counts adjusted for the risk group based on anemia, visceral metastasis, progression by bone scan and pain (HR 1.18; 2P = .07) for stratification factors (HR 1.20; 2P = .052) or both (HR, 1.20; 2P = .046). Men with ≥grade 3 neutropenia and ≥30% prostate-specific antigen level decline by day 90 had improved OS compared with men exhibiting neither (HR 0.51; 2P = .014). CONCLUSIONS For patients with mCRPC who received docetaxel, ≥grade 3 neutropenia on day 8 was prognostic for improved OS, which suggests its utility as a pharmacodynamic marker, in this hypothesis-generating analysis. Exploration of dose escalation of docetaxel to attain ≥grade 3 neutropenia on day 8 may be warranted.

Efficacy of docetaxel-based chemotherapy following ketoconazole in metastatic castration-resistant prostate cancer: implications for prior therapy in clinical trials.

OBJECTIVES Abiraterone acetate (AA) is a CYP17 inhibitor of androgen synthesis approved for use following docetaxel for metastatic castration-resistant prostate cancer (mCRPC); evaluation in the pre-docetaxel setting is ongoing. Given that the reported efficacy of AA is lower following docetaxel vs. pre-docetaxel, the potential exists for cross resistance given docetaxels partly androgen receptor targeting activity. The efficacy of docetaxel following ketoconazole (KC), a weaker and nonspecific inhibitor of CYP17, may provide some insights into this potential interaction. We retrospectively evaluated the efficacy of every 3-week docetaxel with prednisone (DP) in mCRPC previously exposed to KC compared to KC-naive patients. MATERIALS AND METHODS A randomized phase II trial of men with mCRPC treated with DP + AT-101 (bcl-2 inhibitor) vs. DP plus placebo was analyzed. Both arms were combined for analysis as no significant differences were seen. Overall survival (OS), progression-free survival (PFS), objective response (ORR), pain, and prostate-specific antigen (PSA) response rates were estimated with and without prior KC. Cox proportional hazards regression models were used to estimate the effect of covariates on OS. RESULTS Of 220 evaluable men, 40 (18.2%) received prior KC. The median OS with DP-based therapy of KC-naive patients (18.3 months, 95% CI: 15.0, 24.5) and post-KC patients (17.0 months, 95% CI: 9.9, 20.4) was not statistically different (P = 0.20). After controlling for prognostic classifications, analyses demonstrated consistent trends for worsening of OS after KC, with (hazard ratios (HRs) 1.33-1.46. Similar unfavorable trends were observed for ORR, PSA declines, and PFS. CONCLUSIONS In this hypothesis-generating analysis, patients treated with docetaxel-based chemotherapy following prior KC had numerically and consistently worse outcomes than patients not exposed to prior KC. Although the estimated differences did not attain statistical significance, evaluation of outcomes with docetaxel in particular, and all classes of novel and emerging agents following AA, is of clinical importance, given its more potent androgen synthesis inhibition compared with KC. Drug development should take into account the potential impact of previous therapy.

A randomized, double-blind phase II trial of docetaxel plus prednisone (DP) combined with either AT-101 or placebo for the first-line therapy of metastatic castration-resistant prostate cancer (CRPC)

4528 Background: AT-101 (A), a small molecule oral inhibitor of the Bcl-2 protein family has broad preclinical activity including synergy with docetaxel (D). AT-101 has demonstrated activity alone and in combination with D in D-refractory patients with metastatic CRPC. METHODS A randomized, double-blind, placebo-controlled phase II trial was conducted to compare the combination of DP with either A or placebo in chemo-naive men with progressive metastatic CRPC. A key requirement was progression (bone scan, RECIST or rising PSA ≥ 2 ng/mL) despite androgen deprivation. Stratification factors were pain and performance status. Patients received DP (75mg/m2 day 1; 5mg PO b.i.d.) Q 21 days (1 cycle) with either A (40 mg b.i.d.) or placebo PO on days 1-3. Radiological assessments were performed every 3 cycles. Primary endpoint was overall survival (OS) and 221 patients were planned for 110 events (80% power, HR 0.67, 1-sided alpha 0.1). RESULTS 221 patients were randomized and baseline factors were balanced in the 2 groups. Median OS for patients on ADP was 17.8 months vs. 17.5 months for Placebo-DP (HR 1.06, 95% CI 0.72-1.55). The median PFS was 11.0 months and 10.3 months for ADP and Placebo-DP arms respectively (HR 0.88, 95% CI 0.63, 1.22). PSA reductions of ≥50% or ≥30% were seen in 54% and 66% of ADP treated patients compared to 46% and 54% of controls, respectively. Measurable disease control rates for ADP and placebo-DP were 93% and 80%, respectively. Grade 3/4 AEs that occurred with higher incidence in the AT-101 arm of the trial compared to placebo included cardiac AEs (5% v 2%), lymphopenia (23% v 16%), neutropenia (47% v 40%), ileus (2% v 0%) and pulmonary embolism (6% v 2%). The incidence of grade 1/2 peripheral neuropathy was 24% vs. 13%. In a subgroup of patients with poor-risk CRPC (n=34), efficacy endpoints favored ADP (median OS 19 vs.14 months). CONCLUSIONS The combination of AT-101 with DP in men with chemonaive metastatic CRPC was well tolerated but did not extend OS compared to placebo-DP. There was a potential benefit in a subset of high-risk patients.

Neutropenia as a potential pharmacodynamic marker for docetaxel-based chemotherapy in men with metastatic castration-resistant prostate cancer (mCRPC).

51 Background: Data suggest docetaxel clearance is increased in castrate men. An association of docetaxel-induced grade ≥3 neutropenia with overall survival (OS) may provide a rationale for tailored dosing in mCRPC. METHODS The association of cycle 1 neutropenia with OS was examined in a randomized phase II trial of 221 men with mCRPC receiving docetaxel-prednisone combined with placebo or AT-101 (bcl-2 inhibitor), which performed weekly blood cell counts during the first cycle. Patients from both arms were combined as no outcome or neutropenia differences were observed. OS was calculated from randomization by the Kaplan-Meier method and Cox proportional hazards regression models were used to estimate the association with OS. RESULTS The difference in OS between men with day 8 ≥grade 3 neutropenia and those with ≤grade 2 neutropenia was significant after adjusting for stratification factors (HR: 0.64, p= 0.048). Excluding men with delayed cycle 2 yielded a more significant association of grade 3-4 neutropenia on day 8 with survival (Table). Men with ≥grade 3 neutropenia and ≥30% PSA decline by day 90 had improved OS compared with men exhibiting neither (HR: 0.51, p=0.014). CONCLUSIONS In mCRPC receiving docetaxel, ≥grade 3 neutropenia on day 8 was prognostic for improved OS, suggesting its potential utility as a pharmacodynamic marker in this hypothesis-generating analysis. Since the association was stronger after excluding patients that experienced dose delays, grade 3 neutropenia may confer a more favorable therapeutic index than grade 4 neutropenia. The exploration of dose modulation of docetaxel to attain ≥grade 3 neutropenia on day 8 may be warranted. [Table: see text].

Efficacy of docetaxel and prednisone in men with metastatic castration-resistant prostate cancer (mCRPC) exposed to prior ketoconazole (KC).

204 Background: The efficacy of docetaxel following exposure to androgen synthesis inhibitors such as KC or abiraterone acetate (AA) is unknown. Given the emerging use of pre-docetaxel AA and docetaxels inhibition of androgen signaling, we retrospectively evaluated the efficacy of every 3 week docetaxel with prednisone (DP) in mCRPC previously exposed to KC as compared to KC-naïve patients. METHODS A randomized phase II trial of men with mCRPC treated with DP+AT-101 (bcl-2 inhibitor) vs. DP+placebo was analyzed (stratified for pain and performance status). Both arms were combined for analysis as no significant differences were seen. Overall survival [OS], progression-free survival [PFS], objective response [ORR], pain and PSA response rates were estimated with and without prior KC. RESULTS Of 220 evaluable men, 40 (18.2%) received prior KC (median duration=2.0 months, maximum=31.1 months). These 40 men had less visceral disease (15% vs 28%), more prior radiotherapy (70% vs 51%), and increased prior radiological (38% vs 21%) or bone scan progression (55% vs 41%). Efficacy outcomes were not statistically different (table). After adjusting for baseline stratum and treatment group, prior KC did not appear to significantly change OS with DP-based therapy (HR 1.34, 95%CI: 0.86-2.09, p=0.20). CONCLUSIONS Similar outcomes were observed in mCRPC treated with DP-based therapy with or without prior KC. Given the marginally inferior survival with prior KC, evaluation of docetaxel outcomes following AA is of clinical importance, given its more potent CYP17 inhibition. [Table: see text].

Abstract LB-204: Highly potent and optimized small-molecule inhibitors of MDM2 achieve complete tumor regression in animal models of solid tumors and leukemia.

Activation of p53 by blocking the interaction of MDM2-p53 using non-peptide small-molecule inhibitors is being pursued as a promising new cancer therapeutic strategy. Although genetic activation of p53 has been shown to achieve complete tumor eradication in mice, the best small-molecule inhibitors of the MDM2-p53 interaction reported to date (Nutlins including RG7112 or first generation spiro-oxindoles such as AT219) can only inhibit tumor growth but fail to achieve significant tumor regression in animal models of human cancer. In the present study, we demonstrate, for the first time, that 2 highly optimized spiro-oxindole compounds, Compound A and Compound B, are capable of achieving complete tumor regression or even permanent cure in multiple xenograft models of human cancer (sarcoma, leukemia, prostate) without causing any significant signs of toxicity to animals. They bind to human MDM2 protein with Ki values of Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-204. doi:10.1158/1538-7445.AM2011-LB-204