Cell cycle arrest: A breakthrough in the supportive care of older cancer patients

Age is a major risk factor for the acute and chronic complications of cancer chemotherapy. The current approach to the prevention of these complications is reactive and involves the reduction of the doses and the delay of treatment which may compromise the outcome. There is a limited number of antidotes to chemotherapy toxicity and these have complications of their own. Oldest old and frail patients are mostly excluded from life saving cancer treatment due to the risk of severe and even lethal complications.

molecular biology has revealed that different checkpoints control the proliferative cycle of normal and neoplastic cells. Two new drugs, Trilaciclib and ALRN-6924 may cause a temporary cell cycle arrest (CCA) of normal cells without blocking the proliferation of the neoplastic ones and render the normal cells temporarily invulnerable to the toxicity of chemotherapy. We reviewed the publications related to these drugs on the Medline, the published drug information and the presentations to major medical conferences.

In three randomized controlled phase II trials Trilaciclib proved effective in preventing neutropenia, thrombocytopenia and anemia in patients with non small cell lung cancer with non proficient RB1 gene. Forty-five percent of patients were 65 and older and age did not prevent the effectiveness of the drug. Trilaciclib was approved by the FDA for the management of these patients. ALRN-6924 appeared promising in preventing myelotoxicity in patients whose cancer had deleted or mutated TP53, but failed to show any significant activity in a randomized controlled study. The development of this drug is now on hold CONCLUSIONS: CCA is a novel proactive approach to the toxicity of chemotherapy of special interest to older patients. At the very least it may prevent all forms of myelotoxicity with a single agent, obviating the risk and cost of polypharmacy. It allows to avoid the complications of myelopoietic growth factors which include severe pain, stem cell competition, bone marrow exhaustion, and hematological malignancies. It may allow the treatment of frail patients with full chemotherapy doses. It is also reasonable to expect that may complications other common and sometimes lethal complications of chemotherapy such as stomatitis, esophagitis, diarrhea and dehydration.