The Food and Drug Administration (FDA) has approved trilaciclib (Cosela; G1 Therapeutics, Inc.) as a protectant to decrease the incidence of chemotherapy-induced myelosuppression in adults receiving a platinum- or etoposide-containing chemotherapy regimen or a topotecan-based intervention for the treatment of extensive-stage small cell lung cancer (ES-SCLC).1

The regulatory decision is based on data from 3 randomized, placebo-controlled trials (N=245) that demonstrated a clinically meaningful and statistically significant reduction in the duration and severity of neutropenia among adults with ES-SCLC who received trilaciclib prior to chemotherapy initiation. Findings from the 3 investigations — G1T28-02 (NCT02499770), G1T28-05 (NCT03041311), and G1T28-03 (NCT02514447) — associated trilaciclib administration with a lower risk for severe neutropenia vs placebo. Trilaciclib also correlated with a shorter neutropenia duration among trilaciclib recipients who experienced neutropenia compared with patients in the placebo group.2

Trilaciclib was found to be well-tolerated, with most adverse events (AEs) of mild to moderate severity. Serious AEs were observed in 30% of patients who received trilaciclib, and grade 3 or 4 hematologic AEs were seen more commonly among patients who received placebo in place of trilaciclib. Specifically, grade 3/4 hematologic AEs included neutropenia (32%, trilaciclib vs 69%, placebo), febrile neutropenia (3% vs 9%), anemia (16% vs 34%), thrombocytopenia (18% vs 33%), and leukopenia (4% vs 17%).1 

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G1T28-02, G1T28-05, and G1T28-03 specifically studied trilaciclib’s efficacy in patients scheduled to receive carboplatin- or etoposide-based chemotherapy regimens with or without atezolizumab, as well as topotecan-based interventions. The pool of 245 patients was randomly assigned to receive either trilaciclib or placebo prior to chemotherapy initiation.1,2

Notably, trilaciclib is the first therapy in its class to reduce the frequency of chemotherapy-induced bone marrow suppression in this patient population and is intravenously administered as a 30-minute infusion 4 hours before chemotherapy initiation. The agent is thought to induce its protective effect by inhibiting the CDK 4/6 enzyme, thereby preserving bone marrow cells.2

“For patients with ES-SCLC, protecting bone marrow function may help make their chemotherapy safer and allow them to complete their course of treatment on time and according to plan,” Albert Deisseroth, MD, PhD, supervisory medical officer in the Division of Non-Malignant Hematology at the FDA’s Center for Drug Evaluation and Research, said in a press release. “Today’s approval of [trilaciclib] will give patients a treatment option that can reduce the occurrence of a common, harmful side effect of chemotherapy.”

The FDA recommends that providers advise patients of the potential for injection site reactions, acute drug hypersensitivity, interstitial lung disease/pneumonitis, and embryo-fetal toxicity with trilaciclib therapy.


  1. FDA approves G1 Therapeutics’ Cosela™ (Trilaciclib): the first and only myeloprotection therapy to decrease the incidence of chemotherapy-induced myelosuppression [press release]. Research Triangle Park, NC: G1 Therapeutics, Inc.; February 12, 2021.
  2. FDA Approves Drug to Reduce Bone Marrow Suppression Caused by Chemotherapy [press release]. Silver Spring, MD: FDA; February 12, 2021.