Novartis has announced positive long-term results from the Phase 3 ASC4FIRST clinical trial, demonstrating that its Chronic Myeloid Leukemia (CML) treatment, Scemblix (asciminib), continues to deliver superior efficacy compared with currently available standard-of-care Tyrosine Kinase Inhibitors (TKIs). The findings were presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting.

The latest 144-week data provide evidence of sustained treatment benefit in adults newly diagnosed with Philadelphia chromosome-positive chronic myeloid leukemia in chronic phase (Ph+ CML-CP). According to the company, Scemblix showed increasingly higher rates of major molecular response (MMR) over time when compared with investigator-selected standard therapies, including imatinib, nilotinib, dasatinib and bosutinib.

The ASC4FIRST study evaluated Scemblix against both standard-of-care TKIs and imatinib alone in 405 newly diagnosed adult patients. Results revealed that the gap in treatment response continued to widen in favour of Scemblix over nearly three years of follow-up.

At week 144, Scemblix-treated patients achieved significantly higher MMR rates than those receiving standard treatments. Nearly 24 percent more patients achieved MMR compared with the overall standard-of-care group, while the advantage over imatinib alone exceeded 32 percent. The therapy also demonstrated a meaningful benefit over second-generation TKIs, with an MMR rate of 75 percent compared with 59.8 percent in the comparator group.

Beyond major molecular responses, patients receiving Scemblix achieved deeper molecular responses, including MR4 and MR4.5, indicating stronger suppression of disease activity.

The treatment also demonstrated superior patient retention. At the 144-week mark, a significantly higher proportion of patients remained on Scemblix therapy compared with those receiving standard treatments, suggesting improved long-term tolerability and treatment adherence.

Dr. Jorge Cortes, Chief of Hematology at the UAB O’Neal Cancer Center, noted that because CML is typically a lifelong condition requiring prolonged treatment, therapies must combine strong efficacy with favourable safety and tolerability. He said the extended data showed Scemblix continued to deliver superior response rates compared with both first- and second-generation TKIs.

Mark Rutstein, Global Head of Oncology Development at Novartis, said the company’s long-standing commitment to advancing CML treatment has contributed to the development of Scemblix. He added that nearly three years of follow-up data further strengthen confidence in the therapy as an important option for newly diagnosed patients.

Safety findings from the trial remained consistent with previous studies, with no new safety concerns identified. Compared with both imatinib and second-generation TKIs, Scemblix was associated with fewer severe adverse events, fewer treatment modifications required to manage side effects, and more than 50 percent lower treatment discontinuation rates due to adverse reactions. Common side effects included diarrhoea, headache, fatigue, musculoskeletal pain and skin rash.

Scemblix is the first CML treatment designed to specifically target the ABL myristoyl pocket, a mechanism known as STAMP (Specifically Targeting the ABL Myristoyl Pocket). This approach differs from conventional TKIs, which work by targeting the ATP-binding site of the BCR-ABL protein.

The drug has already received accelerated approval in the United States for newly diagnosed adult patients with Ph+ CML-CP and is approved in more than 60 countries, including the European Union, China and Japan. It is also approved for previously treated CML patients and those carrying the T315I mutation in multiple markets worldwide.

Novartis stated that despite major advances in CML treatment over the past 25 years, challenges such as treatment resistance, intolerance and failure to achieve optimal response remain significant. The company continues to focus on developing more targeted therapies that improve outcomes and quality of life for people living with the disease.

The ongoing ASC4FIRST trial will continue to generate additional efficacy and safety data as Novartis seeks to further establish Scemblix’s role in the frontline treatment of chronic myeloid leukemia.