The investigational drug asciminib (being developed by Novartis) may become the new kid on the block for the treatment of chronic phase chronic myeloid leukemia (CMP-CP) for patients who have relapsed on or are refractory to at least two prior tyrosine kinase inhibitors (TKIs).
New results from the ASCEMBL study (NCT03106779) show that patients who received asciminib, which works differently from currently approved therapies for CML-CP, achieved better responses, compared with bosutinib (Bosulif) as third-line therapy.
“The ASCEMBL study opens a new chapter for CML, proving comparatively superior efficacy and excellent safety for a new class of ABL inhibitors,” coinvestigator Michael J. Mauro, MD, from Memorial Sloan Kettering Cancer Center, New York, said in an interview.
The trial was presented as a late-breaking abstract at the annual meeting of the American Society of Hematology.
Asciminib is a first-of-a-kind STAMP (Specifically Targeting the ABL Myristoyl Pocket) inhibitor that works differently from currently approved TKIs, which are adenosine triphosphate (ATP)-–competitive ABL inhibitors.
Five TKIs have been approved by the Food and Drug Administration to treat CML: imatinib (Gleevec; generics), nilotinib (Tasigna), dasatinib (Sprycel), bosutinib, and ponatinib (Iclusig).
All of them inhibit BCR/ABL tyrosine kinase by binding to the ATP-binding pocket.
Most patients with TKI resistant disease develop mutations in the ATP-binding pocket, explained Michael Jay Styler, MD, associate professor at Fox Chase–Temple University Hospital bone marrow transplant program, Fox Chase Cancer Center, Philadelphia.
By inactivating the protein through binding outside the ATP site, asciminib is a novel BCR-ABL inhibitor and may be a superior alternative to further traditional TKIs. “This agent promises to be an important addition to our treatment armamentarium for CML,” Dr. Styler said in an interview.
Another expert agreed. “Although we have many excellent therapies for CML, having a new medication that targets BCR-ABL in a novel way is still welcome to help us better care for CML patients,” Gabriela S. Hobbs, MD, said in an interview. Dr. Hobbs is the clinical director of leukemia services at Boston’s Mass General Cancer Center.
Patients in this study had previously been receiving at least two different types of TKIs. “The responses looked very encouraging for this group of heavily pretreated patients. Although CML patients do very well on current therapies, those that don’t get a response with TKI remain a difficult clinical challenge,” Dr. Hobbs said.
“This is the first study comparing asciminib to a TKI directly (in this case bosutinib) and it showed safety as well as preliminary evidence of efficacy. I look forward to seeing additional studies with this promising drug and to have a new drug to add to the CML arsenal,” she added.
Identifying patients who will benefit from asciminib
Patients with CML are currently sequenced through more than one second-generation TKI, Dr. Mauro commented. “If imatinib and a second-generation TKI have not served a patient well, only bosutinib has been studied in the third line and comparatively in the ASCEMBL study.” Asciminib was shown to be superior and could offer a clear alternative to ponatinib, which would be the other choice and is typically given even later after sequencing all other available options.
Dr. Hobbs agreed. “This is a challenging group of patients to manage as their options are limited. Ponatinib is often the drug of choice in these scenarios, as well as bone marrow transplant.”
They also agreed that it may be effective (alone or in combination) in treating patients with T315I-mutation CML, which is a particularly challenging disease.
Senior study author Andreas Hochhaus, MD, of the Klinik für Innere Medizin II in Jena, Germany, who presented the data at the meeting, noted new trials to test the efficacy of asciminib alone or in combination in earlier lines of therapy are ongoing and include the investigator-initiated FASCINATION study (first-line asciminib in combination) in Germany (NCT03906292).