GTx Says Enobosarm Late-stage Trials Failed To Meet Overall Criteria - Update

(RTTNews) - GTx, Inc. (GTXI) Monday said its two enobosarm clinical trials in patients with non-small cell lung cancer or NSCLC receiving chemotherapy, failed to meet the overall criteria for the co-primary responder endpoints of lean body mass and physical function. The stock plunged more than 68 percent in pre-market activity.

A 3 mg dose of enobosarm was studied in two Phase 3, placebo-controlled, double blind clinical trials to prevent and treat muscle wasting in patients with NSCLC. In each trial, 325 patients with stage III or IV NSCLC were randomized to oral daily doses of placebo or enobosarm 3 mg when they began first-line standard platinum doublet chemotherapy.

The trials were designed to assess the response rates of enobosarm compared to placebo for the co-primary endpoints at 3 months of treatment on maintenance or improvement of total lean body mass (muscle) assessed by Dual-energy X-ray Absorptiometry and improvement in physical function measured by the stair climb test.

The responder endpoints in the trials, known as the POWER trials, showed mixed results. Initial exploratory quantitative analysis showed that enobosarm had a consistent effect on lean body mass or LBM relative to placebo in both studies at all assessment times.

Corresponding analyses for stair climb power or SCP were inconsistent between trials. Missing data were well balanced between the arms in both trials for both endpoints, Gtx noted.

Enobosarm was generally well tolerated in both clinical trials. The occurrence of serious adverse events and overall incidence of adverse events were similar across placebo and treatment groups.

In POWER1, the four most common adverse events reported were nausea, loss of hair, anemia and vomiting.

In POWER2, the four most common adverse events were anemia, nausea, neutropenia and vomiting. In the safety analysis of survival, there was no evidence of difference between patients treated with enobosarm and placebo in either clinical trial.

GTx plans to discuss the future course of action with both the FDA and European regulatory authorities.

Mitchell Steiner, CEO of Gtx, said, ''While we are disappointed that both studies did not meet the pre-specified responder analyses, we are encouraged by the unambiguous effect of enobosarm on muscle and we are confident that it will translate to clinical benefit and potentially increase survival in patients with non-small cell lung cancer."

GTXI, which closed at $4.15 on Friday, is plunging 68.2 percent in pre-market activity.