CLL/SLL is a hematologic malignancy caused by mature B-cell neoplasms. It primarily affects older populations and is among the most common leukemia subtypes in the Western World, with over 100,000 new diagnoses reported globally each year1. In China, where the incidence rate of CLL/SLL is lower than that of the western countries, the disease is occurring at a rapidly rising rate, with a younger age of onset and higher aggressiveness2. SLL and CLL are two different manifestations of the same disease and approximately 20% of all SLL cases would progress to CLL3. Treatments such as immunotherapies and Bruton's tyrosine kinase inhibitors (BTKis) have significantly improved patients’ responses to initial treatment. However, due to the limitations of existing treatment options, the poor prognosis of patients, severe impact on patients’ quality of life and high complexity of the disease, patients with r/r CLL/SLL are in desperate need for new treatment options that are safe and effective.
The introduction of Bcl-2 inhibitors has further revolutionized the treatment of CLL/SLL. Bcl-2 is an apoptosis suppressor factor that regulates cell survival by controlling mitochondrial membrane permeability. It suppresses apoptosis by inhibiting the release of cytochrome C from mitochondria or by binding to apoptotic activators to inhibit the activity of caspase. The overexpression of Bcl-2, found in a variety of hematologic malignancies, particularly CLL/SLL, is a key mechanism by which tumor cells evade apoptosis.
However, the development of Bcl-2 as a therapeutic target is challenging mainly because its mechanism of action is based on the protein-protein interaction (PPI). The binding interface of Bcl-2 is relatively large, making it difficult for small-molecule inhibitors to exert blocking effects. Additionally, the Bcl-2 protein is located on the mitochondrial membrane, and mitochondria, with its double-membrane structure, is among the most complex and challenging cellular components. Drugs must first penetrate the cell membrane before they can further act on the mitochondrial membrane. In nearly 40 years since the discovery of this target, only one Bcl-2 inhibitor has been approved globally, a reality highlighting the immense difficulty and challenges in this field of research and development. In western countries, the treatment of CLL/SLL has entered a new era of chemotherapy-free and fixed-duration regimens, while no Bcl-2 inhibitor has been approved in China in this therapeutic area. Therefore, patients in China have an urgent unmet need for such novel therapies that can offer both efficacy and safety.
Lisaftoclax is a novel, investigational orally administered small-molecule Bcl-2 selective inhibitor being developed by Ascentage Pharma to treat patients with malignancies by selectively blocking the antiapoptotic protein Bcl-2 and hence restoring the normal apoptosis process in cancer cells. Lisaftoclax is the first Bcl-2 inhibitor in China and the second anywhere globally that has demonstrated compelling clinical benefit and entered a pivotal registrational study. Lisaftoclax has broad therapeutic potential for a variety of hematologic malignancies and solid tumors, particularly as a single agent and in combinations in CLL/SLL. Lisaftoclax is a potential drug that may offer patients a safe, effective, and easy to use treatment option.
Lisaftoclax is being evaluated in multiple registrational Phase III studies, including a global registrational Phase III study of lisaftoclax in combination with a BTKi in previously treated patients with CLL/SLL (cleared by the US FDA); a global registrational Phase III study of lisaftoclax in combination with acalabrutinib for the first-line treatment of treatment-naïve patients with CLL/SLL; a global registrational Phase III study of lisaftoclax in combination with azacitidine (AZA) for the first-line treatment of elderly/unfit treatment-naïve patients with acute myeloid leukemia (AML) who were intolerant of standard induction chemotherapies; and a global registrational Phase III study of lisaftoclax in combination with AZA for the first-line treatment of newly-diagnosed patients with higher-risk myelodysplastic syndrome (MDS).