G1 Therapeutics Inc (NASDAQ: GTHX) stock plummet 42.57% on December 20th, 2018 (Source: Google finance) after the company said one of its drugs met endpoints in a clinical study but had not done as well as other metrics versus a placebo treatment. The company is developing trilaciclib, a cell-preserving drug it hopes to position for use alongside chemotherapy in cancer patients. If the drug can successfully preserve cells usually destroyed by chemotherapy, it could significantly reduce patient burden and improve outcomes.
The company said a mid-stage clinical trial showed that the use of its drug trilaciclib with another cancer drug in small-cell lung cancer patients significantly reduced the duration and instances of Grade 4 neutropenia, or a low white blood cell count which can result in infections. However, the company also reported that in other metrics, the treatment was less effective than in patients given a placebo treatment. G1 said patients given the treatment had an “objective response rate” of 13.3% versus 23.1% in the placebo group, and a “clinical benefit rate” of 60% versus 61.5% in the placebo group. The company now have four randomized Phase 2 trials showing trilaciclib’s multi-lineage myelopreservation benefits and the company plan to meet with U.S. and European regulatory authorities in 2019 to discuss the totality of trilaciclib data and pathways to approval.
Meanwhile, GTHX had announced positive topline data showing multi-lineage myelopreservation benefits in its randomized, double-blind, placebo-controlled Phase 2 trial evaluating trilaciclib in combination with topotecan as a treatment for 2nd-/3rd-line small cell lung cancer (2/3L SCLC). The Phase 1 dose finding portion of this trial enrolled 32 patients. The randomized, double-blind, placebo-controlled Phase 2 portion of the trial enrolled 91 patients with SCLC who had received 1-2 prior lines of therapy. In the three-arm trial, all patients received a chemotherapy regimen of topotecan. Patients were randomized to receive topotecan (1.5 mg/m2) + placebo, or one of two approved doses of topotecan (1.5 mg/m2 or 0.75 mg/m2) + trilaciclib (240 mg/m2). Treatment for all three arms was administered intravenously on Days 1 through 5 of a 21-day cycle. The standard therapeutic dose of topotecan is 1.5 mg/m2; the 0.75 mg/m2 dose was also included in this trial in order to define the appropriate combination regimen of topotecan and trilaciclib. It was determined that 1.5 mg/m2 is the appropriate dose of topotecan when administered in combination with trilaciclib, and key trial findings reported below compare the 1.5 mg/m2 topotecan + placebo arm to the 1.5 mg/m2 topotecan + trilaciclib arm