“In the ASC4FIRST trial, asciminib is the first and only agent to demonstrate statistically significant efficacy versus standard-of-care frontline TKIs in newly diagnosed CML patients,” said senior author Jorge E. Cortes, MD, director of the Georgia Cancer Center at Augusta University in Georgia, in presenting the findings at a press briefing for the annual meeting of the American Society of Clinical Oncology (ASCO) in Chicago.
”Asciminib’s strong benefit-risk profile may transform the CML treatment paradigm,” Dr. Cortes said.
The study was published concurrently in The New England Journal of Medicine.
While TKIs have transformed the treatment of CML, improving the 5-year survival rates from 22% in the 1970s to 70% in recent years, nearly half of patients do not achieve a major molecular response within a year, due to either resistance or intolerance, causing the common switching of drugs.
Long-term use is further associated with common side effects, including gastrointestinal and cardiovascular events, due to off-target effects.
Asciminib is a potent and highly specific agent is an allosteric inhibitor targeting ABL myristoyl pocket, which is important in avoiding off-target effects that cause the common side effects.
The drug already has approval from the US Food and Drug Administration (FDA) for the treatment of patients with chronic phase CML who are resistant or intolerant to at least 2 prior TKIs or those with T315I mutation.
For the current pivotal phase 3 ASC4FIRST trial to evaluate the drug as a frontline therapy in recently diagnosed patients with chronic phase CML, 405 patients from cancer centers in 29 countries were enrolled.
The participants were randomized to treatment either with asciminib 80 mg once daily (n = 201) or to an investigator-selected TKI (n = 204), determined based on factors including patient age, preference, and overall health.
In the latter group, 102 patients were receiving imatinib and an equal number receive a stronger, second-generation TKI.
Overall, the patients had a median age of 52 and 65% were male. About 54% were White and 44% were Asian. Those receiving second-generation TKIs were more likely to be younger and without additional health concerns, allowing them to tolerate the more potent drugs.
The median follow-up was 16.3 months in the asciminib group and 15.7 months in the other TKIs group.
For the primary outcome, a major molecular response occurred at week 48 among 67.7% of patients in the asciminib group, compared with 49% in the combined TKI arm of imatinib and second-generation TKI groups (P < .001).
In a subanalysis of patients who were randomized to receive imatinib, a major molecular response occurred at week 48 in 69.3% in the asciminib group versus 40.2% of patients in the imatinib arm (P < .001).
The corresponding rates in the comparison of patients on second-generation TKIs were 66.0% and 57.8%, which was not a statistically significant difference.
Furthermore, a deep molecular response, which may lead to remission and discontinuation of treatment, occurred at week 48 in among 38.8% in the asciminib arm compared with the 20.6% in the combined investigator-selected TKI arm.
In the imatinib comparison analysis, the deep molecular response occurred in 42.6% of patients in the asciminib arm versus 17.8% in the imatinib arm, and in the second-generation TKI arm, the deep molecular response occurred in 35% versus 26.5%, respectively.
Importantly, in the TKI-treated group, significantly more patients in the asciminib group — 86%, remained on therapy at the data cut-off, compared with 62% of those receiving imatinib and 75% of those receiving a second generation TKI.
Adverse events of grade 3 or higher that led to discontinuation were lower with asciminib versus imatinib and second-generation TKIs (38% vs 44.4% and 54.9%, respectively), as were events leading to discontinuation (4.5% versus 11.1% and 9.8%, respectively).
The most common adverse events occurring with asciminib were low platelet count (13%) and low neutrophil count (10%). In terms of severe side effects, blood clots, a known severe side effect of TKIs, occurred in only 1% of patients.
In addition, dose adjustments and treatment interruptions were also more significantly less common in the asciminib group.
Overall, the results indicate that “asciminib has the potential to become a therapy of choice for patients with newly diagnosed chronic phase CML,” said first author Timothy P. Hughes, MD, of South Australian Health and Medical Research Institute and University of Adelaide, Australia, in presenting the findings.
Commenting on the study in an interview, Dr. Cortes underscored the importance of molecular responses as indicators of longer-term responses.
“Early responses correlate with better long-term outcomes,” he said. “Most importantly, they are associated with better probabilities of having a deep molecular response, a requirement for considerations of treatment discontinuation,” which is a highly desirable goal for many patients, he noted.
“If we can get more patients to be eligible for treatment discontinuation and to discontinue successfully, this could be a major advance,” Dr. Cortes emphasized.
“Also, for the patients who do have to stay on therapy for the rest of their lives, a treatment option that has fewer adverse events would be very desirable,” he said.
“We need to see that longer follow-up confirms the current trends, but we are very encouraged by what we see so far.”