G1 Therapeutics Inc. shares skyrocketed 25% in the extended session Monday after the company said it expects to file a new-drug application for its trilaciclib, a drug designed to protect bone marrow from the effects of chemotherapy. That's based on feedback from a meeting with the U.S. Food and Drug Administration and discussion with European regulators, G1 said in a statement. "We look forward to continuing a collaborative dialogue regarding the marketing applications, as well as discussing further clinical development of trilaciclib," Chief Medical Officer Raj Malik said in the statement. Chemotherapy is an effective and important weapon against cancer, but it does not differentiate between healthy cells and cancer cells and kills both, including important stem cells in the bone marrow; trilaciclib has demonstrated in trials the ability to protect bone marrow from chemotherapy damage, the company said in the statement. Shares of G1 ended the regular trading day down 0.2%.