AT WCLC 2016

VIENNA (FRONTLINE MEDICAL NEWS) – The addition of ganetespib to docetaxel for the treatment of advanced non–small cell lung cancer (NSCLC) did not live up to its earlier promise of improved efficacy over docetaxel alone in a phase III study.

Interim results of the GALAXY-2 study, which led to the trial’s termination for futility, showed that there was no difference in the primary endpoint of overall survival (OS). The median OS was a respective 10.9 months and 10.5 months for the combination of ganetespib plus docetaxel versus docetaxel alone (hazard ratio, 1.111, 95% confidence interval, 0.899-1.372, P = .03293).

Median progression-free survival (PFS) was also no different, comparing the ganetespib/docetaxel and docetaxel arms at 4.2 vs. 4.3 months, respectively (HR, 1.161; 95% CI, 0.961-1.403; P = .01186).

The combination had looked promising in the phase II GALAXY-1 study ( Ann Oncol. 2015;26:1741-8 ), with a trend towards improved PFS and OS, with patients diagnosed with advanced disease perhaps gaining the most benefit.

“The addition of ganetespib to docetaxel did not result in improved efficacy for the salvage therapy of patients with advanced-stage lung adenocarcinoma,” Rathi Pillai, MD, said at the World Conference on Lung Cancer.

“Based on these findings, further development of Hsp [heat shock protein] 90 inhibitors in lung cancer should be limited to patients with driver mutations with relevant client proteins,” added Dr. Pillai of the Winship Cancer Institute at Emory University in Atlanta.

In GALAXY-2, 672 patients were randomized, 1:1, to receive docetaxel (75 mg/m2 on day 1) with ganetespib (150 mg/m2 on days 1 and 15) or a placebo every 3 weeks. The median number of cycles received was five in the combination arm and four in the docetaxel-only arm. All patients had advanced non–small cell lung adenocarcinoma diagnosed at least 6 months prior to enrollment and had received only one prior treatment regimen.

Response rates were similar between the two groups, with 13.7% and 16% of ganetespib/docetaxel– and docetaxel/placebo–treated patients achieving a partial response (P = .448) and 56.1% and 50.1%, respectively, having stable disease (P = .123).

Almost two-thirds (65%) of patients given ganetespib/docetaxel reported any grade 3-4 adverse event versus 54% of patients given docetaxel/placebo. The most frequent treatment-emergent grade 3-4 adverse event was neutropenia, occurring in 34.6% ad 29.5% of patients in each arm (P = .1807), with only diarrhea (46.2% vs. 14.6%; P less than .0001) and weight loss (11.3% vs. 5.2%; P = .0044) occurring more frequently in the combination than the docetaxel-only arm.

“With the negative results of this phase III trial and the discontinuation of ganetespib development, is this the end for this once-promising drug class in NSCLC?” asked the discussant for the trial David R. Gandara, MD, of the University of California, Davis, Comprehensive Cancer Center in Sacramento.

Ganetespib is a second-generation Hsp90 inhibitor and the rationale for using Hsp90 inhibitors as cancer therapy remains sound, Dr. Gandara maintained. One of the issues is finding a biomarker to predict the benefit for these drugs in a clinical setting, he said. In the phase II GALAXY-1 trial it was noted that patients diagnosed with advanced disease more than 6 months prior to study entry fared better than those with more recent diagnosis if they were treated with ganetespib/docetaxel than docetaxel alone. Patients with elevated levels of lactate dehydrogenase (eLDH) also seemed to do better than those with normal LDH levels if they were treated with the combination.

These two subpopulations were specifically looked at the in the phase III study, but again no differences in OS or PFS were observed, nor were differences observed in any of the other subgroups analyzed, which included EGFR- and ALK-negative patients, by response rate or progression because of new metastatic lesions.

“Were these the right surrogates to use as predictive biomarkers for heat shock protein inhibition? Of course, in retrospect, it is easy to say that they were not,” Dr. Gandara said.

“Is there still an opportunity for this class of drugs to make a meaningful impact in NSCLC? In my own opinion I think the answer is yes, but not in this broad page approach and not with these potential surrogates as were used in GALAXY-2,” he said at the meeting sponsored by the International Association for the Study of Lung Cancer.

The study was sponsored by Synta Pharmaceuticals, which became part of Madrigal Pharmaceuticals in June 2016. Dr. Pillai reported having no financial disclosures. Dr. Gandara disclosed that he had received research grants from several pharmaceutical companies.