G1 Therapeutics Inc.'s stock dropped by about 40% on Dec. 20 after its lung cancer drug trilaciclib met a goal of preserving white blood cells in a mid-stage trial but failed to surpass placebo based on other metrics of the study.
The Research Triangle Park, N.C.-based biopharmaceutical company evaluated trilaciclib in combination with chemotherapy topotecan against placebo plus topotecan in a phase 2 trial to treat patients with small cell lung cancer who had received two or three prior treatments.
G1 said the trial met its main goal of reducing the duration and occurrence of events related to neutropenia — a condition in which a person has a low level of neutrophils, a type of infection-fighting white blood cells that are made in the bone marrow. The trilaciclib combo showed a 75.9% reduction in such events compared to 40.6% for those on placebo.
Trilaciclib also resulted in a 45% reduction in the number of Granulocyte-colony stimulating factor or, G-CSF, administrations per treatment cycle compared to placebo. G-CSF are proteins that help the bone marrow produce white blood cells to reduce the risk of infection after chemotherapy. In addition, the drug combo showed a 58.7% reduction in the number of red blood cell transfusions per week compared to placebo.
But patients on both placebo and the trilaciclib combo lived for about 4.2 months without their disease worsening, which was consistent with previous data. Overall survival data was immature and will be reported later. G1 noted that the treatment was well-tolerated and there were fewer adverse events compared to placebo.
The company said 23% of patients in the placebo arm saw their tumors shrink, compared with 13% for the trilaciclib combo. In terms of the clinical benefit of the combo, placebo beat trilaciclib with a rate of 61% compared with 60%.
G1 is evaluating trilaciclib in a number of different trials, and President and CEO Mark Velleca said the ultimate goal is to get the product approved for use with multiple chemotherapies and with a tumor-agnostic label. The company's chief medical officer and senior vice president of research and development, Raj Malik, said in a Dec. 19 press release that the company has four phase 2 trials showing trilaciclib's benefits in preserving blood cells. The condition, called myelosuppression, is when bone marrow activity is decreased, resulting in fewer red blood cells, white blood cells and platelets.
In November, G1 reported positive data from a phase 2 study which evaluated trilaciclib in combination with Roche Holding AG's Tecentriq and chemotherapy in previously untreated patients with small cell lung cancer. The trial showed improved bone marrow functions for the drug combo.
On the company's call discussing the latest results, Cowen analyst Chris Shibutani asked about the U.S. Food and Drug Administration's updated guidelines on cancer trial goals, which included the role of drugs that act as chemotherapy protectants in improving overall survival rather than just progression-free survival.
Velleca said the company is examining the new guidance and will know more about any implications on the trilaciclib trial once the company meets with U.S. and European regulators in 2019. He noted that the drug has not shown any lack of antitumor efficacy in the four trials that have been undertaken.