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.