- On Monday, G1 Therapeutics Inc. reported positive topline results of a Phase 2a study evaluating its lead candidate in patients receiving chemotherapy as a first-line treatment for small cell lung cancer (SCLC).
- The study found patients taking G1's trilaciclib, which inhibits cyclin-dependent kinases (CDK) 4 and 6, needed significantly less granulocyte colony-stimulating factor and smaller chemotherapy doses than those on placebo.
- Instances of life-threateningly low white blood cell counts were also much higher in the placebo arm than in the experimental arm, indicating that "trilaciclib preserved bone marrow and immune system function from the damaging effects of chemotherapy," according to G1's Chief Medical Officer Raj Malik.
CDK 4/6 inhibitors are already proving to be a highly lucrative class of drug. Pfizer Inc.'s Ibrance (palbociclib), first approved in February 2015, raked in $3.1 billion last year; and Eli Lilly & Co.'s fresh-to-the-market Verzenio (abemaciclib) could eventually fetch $2 billion in annual sales, according to some analysts.
Achieving even a fraction of those sales with trilaciclib would be monumental for a clinical-stage company like G1. There's a void to fill too, given that all CDK 4/6 inhibitors cleared by Food and Drug Administration carry only breast cancer indications. Pfizer, Lilly and Novartis AG are assessing their respective CDK 4/6 inhibitors in lung cancer, but many of the studies are in earlier stages. Lilly also saw Verzenio fail in a Phase 3 study that tested it as a treatment for KRAS mutant lung cancers.
Survival data from the Phase 2a trial of trilaciclib is "still immature," yet promising, according to G1. Overall response rates were 66.7% for trilaciclib versus 62.2% for placebo. (All patients in the placebo-controlled study received standard-of-care etoposide and carboplatin.) Median duration of response was 5.7 months for trilaciclib versus 4.3 months for placebo, and median progression-free survival was 6.2 months and 5.0 months, respectively, across the groups.
What's more, there were no Grade 3 or 4 adverse events related to trilaciclib treatment.
With this latest data in hand, G1 plans to accelerate the timeline for trilaciclib and meet with U.S. and European regulators this year to discuss future development of the drug.
"As you know, our regulatory strategy here is to develop trilaciclib for its myelopreservation benefits," Mark Velleca, G1 CEO, said during a March 5 conference call. "I think any improvement in efficacy — and we are seeing trends in that direction in this trial — we think is going to increase uptake of the product by the oncology community."
G1 is also studying its drug in SCLC patients whose disease progressed after first-line or second-line chemotherapy, as well as metastatic triple negative breast cancer. Preliminary data from those trials should become available in the fourth quarter, according to the company. Another mid-stage study is pairing trilaciclib with Roche AG's Tecentriq (atezolizumab) to treat first-line extensive-stage SCLC. Enrollment for that trial complete ahead of schedule, G1 said.
The North Carolina-based biotech's stock traded at $26.55 per share at Monday's market open, up 5.8% from Friday. Since conducting an initial public offering last May, the company's shares have grown in value more than 75%.