Disappointing phase II antitumor results with a drug that is designed to preserve the bone marrow during chemotherapy have dashed G1 Therapeutics Inc.’s hopes of expanding Cosela’s label to include metastatic colorectal cancer patients, at least for now. Cosela (trilaciclib) is an intravenous-administered transient CDK4/6 inhibitor designed to mitigate the side effects patients experience with current cytotoxic drug regimens used to treat aggressive cancers by offering myeloprotection and by preserving immune system function, so enabling patients to receive chemotherapy for longer and at higher doses.