The U.S. Food and Drug Administration (FDA) has granted accelerated approval to Scemblix (asciminib) by Novartis for the treatment of adult patients with newly diagnosed Philadelphia chromosome-positive chronic myeloid leukemia in chronic phase (Ph+ CML-CP). This approval marks a significant advancement in the treatment landscape for CML, offering a new first-line option with improved efficacy and tolerability.
The accelerated approval is based on data from the Phase III ASC4FIRST trial, a head-to-head study comparing Scemblix to investigator-selected standard of care (SoC) tyrosine kinase inhibitors (TKIs), including imatinib, nilotinib, dasatinib, and bosutinib. The trial demonstrated that Scemblix achieved superior major molecular response (MMR) rates at week 48 compared to both investigator-selected SoC TKIs and imatinib alone.
Superior Efficacy and Favorable Safety Profile
The ASC4FIRST trial results showed that nearly 20% more patients treated with Scemblix achieved MMR compared to those on investigator-selected SoC TKIs (68% vs. 49%, p < 0.001). Furthermore, almost 30% more patients achieved MMR with Scemblix compared to imatinib alone (69% vs. 40%, p < 0.001) at week 48. Scemblix is the first CML treatment to demonstrate superior efficacy alongside a favorable safety and tolerability profile compared to both imatinib and second-generation TKIs.
Specifically, the study reported fewer treatment-related grade =3 adverse reactions (ARs) with Scemblix (25.5%) compared to investigator-selected SoC TKIs (33% and 42%), as well as lower rates of dose reductions (6% vs. 14% and 24%) and ARs leading to treatment discontinuation (4.5% vs. 11% and 9.8%). Patients treated with Scemblix also achieved deeper molecular responses, including MR4, compared to investigator-selected TKIs and imatinib alone (41% vs. 22% and 16%) by week 48.
Addressing Unmet Needs in CML Treatment
While TKIs have transformed CML into a chronic disease, challenges related to efficacy and safety continue to hinder long-term treatment success for many patients. A significant proportion of newly diagnosed patients do not achieve molecular response goals, and many discontinue or switch treatment due to intolerance. Studies indicate that nearly half of CML patients do not meet efficacy milestones (MMR), and almost one in four patients discontinue or switch treatment within one year.
According to Lee Greenberger, Ph.D., chief scientific officer at The Leukemia & Lymphoma Society, "Many patients who are newly diagnosed with CML struggle to navigate this chronic condition and may switch or even stop treatment because of side effects that interrupt their daily lives. That’s why approvals of new first-line treatment options are so important. For patients, finding a medicine that’s right for them at the very beginning of treatment may lead to better long-term disease control with fewer side effects."
Clinical Significance and Future Directions
The FDA's accelerated approval of Scemblix offers a promising new treatment option for newly diagnosed Ph+ CML-CP patients. The ASC4FIRST trial remains ongoing, with the next scheduled analysis at week 96 to evaluate the key secondary endpoint (MMR at week 96) and additional secondary endpoints. Continued approval for this indication may be contingent upon verification and description of clinical benefit from confirmatory evidence.
Jorge Cortes, M.D., director, Georgia Cancer Center, stated, "While there are a range of effective TKIs currently available for newly diagnosed patients, clinicians frequently have had to weigh sacrificing either efficacy or tolerability. In the first-of-its-kind ASC4FIRST trial, Scemblix achieved impressive results across all three parameters of efficacy, safety and tolerability versus all standard of care TKIs. This Scemblix data has the potential to be practice-changing."
This approval was also supported by preliminary data from the phase II ASC2ESCALATE study, which includes Ph+ CML-CP patients who have been previously treated with one prior TKI with discontinuation due to treatment failure, warning, or intolerance. Data will be shared at a future medical meeting.
Scemblix functions as a Specifically Targeting the ABL Myristoyl Pocket (STAMP) inhibitor, a novel mechanism of action in CML treatment, contrasting with traditional ATP-binding site inhibitors.
