AbbVie Inc. has announced new results from a Phase II study of investigational compound venetoclax in patients with acute myelogenous leukemia, or AML. In the study, the venetoclax group showed an overall response rate (ORR) of 15.5%, with one patient achieving a complete response and four patients achieving a complete response with incomplete blood count recovery. A complete response (CR) is sometimes called complete remission, and refers to the disappearance of all signs of cancer in response to cancer treatment.

A complete response with incomplete blood count recovery (CRi) is when a patient fulfills most - but not all - criteria to be classified as a complete response. The Phase II, open-label, multicenter clinical trial was designed to evaluate the preliminary efficacy of venetoclax in 32 patients with relapsed/refractory AML or as frontline therapy for patients who are unfit for intensive therapy. Secondary objectives included safety and pharmacodynamics assessments.

Isocitrate dehydrogenase (IDH) mutations are genetic mutations found in a small number of patients with AML and may influence outcomes. IDH mutations were found in three patients who achieved CR/CRi. Two of these patients also achieved minimal residual disease (MRD) negativity, which represents a response to a given therapy and describes the detection of zero leukemic cells during treatment or after a patient is in remission.

Additionally, researchers assessed patients' bone marrow myeloblast (blast, or immature white blood cells) counts. A bone marrow blast count of greater than 20% is generally required for a diagnosis of AML and reduction of blasts indicate a diminished presence of leukemia. The median bone marrow blast count in evaluable patients treated with venetoclax decreased 36%.