A study from Princess Margaret Cancer Centre has found a potential treatment for patients with relapsed or treatment-resistant acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS), a group of disorders affecting bone marrow function.
AML is an aggressive cancer where immature white blood cells, called myeloblasts, multiply uncontrollably and disrupt the production of healthy blood cells. Outcomes vary based on the types of gene mutations a patient with AML carries.
Although it can be cured in 35 per cent to 40 per cent of patients under the age of 60, and 5 per cent to 15 per cent of patients over 60, those with certain mutations, such as in the tumour protein p53 gene (TP53), have a median overall survival of five months to 10 months.
There is no standard treatment for patients with relapsed or treatment-resistant AML.
MDS syndrome, where the bone marrow does not produce enough healthy blood cells, can vary widely in severity, ranging from mild cases that may not require treatment to more serious forms that can progress to AML. The only curative option for these patients is stem cell transplantation.
A protein called polo-like kinase 4 (PLK4) is dysregulated in several cancers, including AML. PLK4 plays a role in regulating cell division and high levels of this protein are associated with poor survival in AML.
"An inhibitor that targets PLK4, called CFI-400945, was discovered in a prior drug discovery program at UHN," says
Dr. Karen Yee, clinician investigator at the Princess Margaret and senior author of the study.
“Previous research in tumour samples and drug characteristics, such as selectivity, make it a promising candidate for cancer treatment," says Dr. Yee, who is also an associate professor at the University of Toronto. “To examine this candidate, CFI-400945 was tested in tumour models and we conducted a phase I clinical trial in high-risk patients with relapsed and untreatable AML."
The tumour model studies indicated that CFI-400945 is effective, with a treatment response in cells with TP53 mutations, suggesting that PLK4 is a potential therapeutic target in TP53 mutant AML.
The clinical trial was then conducted with 13 individuals with relapsed and treatment-resistant AML. Gene mutation analysis was available for eight of these patients and indicated that four had mutations in TP53. Patients were treated with CFI-400945 at increasing doses from 64 milligrams per day to 128 milligrams per day.
"We found that three out of nine patients evaluated for efficacy saw complete remission," says Dr. Yee. “One other patient showed a greater than 50 per cent improvement in white blood cell counts.
"Additionally, of these four patients, three of them had TP53 mutations."
This study underscores the promising role of CFI-400945 as a potential treatment for a typically challenging form of AML. Manageable side effects, such as enteritis/colitis (inflammation of the small or the large intestine) were noted, indicating a reasonable safety profile.
Moving forward, researchers are investigating CFI-400945's efficacy and safety in larger patient cohorts, as well as in combination with other therapies.
This work was supported by The Princess Margaret Cancer Foundation (PMCF).
Dr. Karen Yee has been a consultant for Bristol Myers Squibb/Celgene, F. Hoffmann-La Roche, GSK, Jazz Pharmaceuticals, Novartis, Pfizer, Shattuck Labs, Taiho Oncology, and Takeda; Dr. Yee received research funding from Astex Pharmaceuticals, Forma Therapeutics, F. Hoffmann-La Roche, Forma Therapeutics, Genentech, Geron Corporation, Gilead Sciences, Janssen Pharmaceuticals, Jazz Pharmaceuticals, Novartis, Shattuck Labs, and Treadwell Therapeutics, and received honoraria from AbbVie, TaiHo, and Novartis. For a full list of competing interests, see article.
