The combination of the BCL2 inhibitor venetoclax with a hypomethylating agent (HMA) may be a treatment option for patients who develop acute myeloid leukemia (AML) secondary to a myeloproliferative neoplasm (MPN), according to results of a small, retrospective cohort study published in Leukemia Research.1
The Philadelphia chromosome-negative MPNs, which include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), are clonal disorders resulting in the proliferation of myeloid cells in the bone marrow. Both PV and ET can progress to secondary myelofibrosis which, along with PMF, can progress to secondary AML, also known as MPN-blast phase (MPN-BP).
Furthermore, MPN-BP, defined in this study as being associated with peripheral or bone marrow blasts of at least 20%, is not sensitive to intensive chemotherapy, and clinical outcomes for patients with this disease are very poor. Median overall survival is only approximately 3 to 5 months, and allogeneic hematopoietic stem cell transplantation (HSCT) is considered the only curative option for these patients.
Venetoclax in combination with an HMA, azacitidine, decitabine, or low-dose cytarabine recently received regular US Food and Drug Administration (FDA) approval for the treatment of adults with newly diagnosed AML who are at least 75 years old or unable to tolerate intensive chemotherapy.2 However, patients with MPN-BP were excluded from the VIALE-A (ClinicalTrial.gov Identifier: NCT02993523) and VIALE-C (ClinicalTrial.gov Identifier: NCT03069352) phase 3 studies evaluating venetoclax in combination with azacitadine and low-dose cytarabine, respectively, in newly diagnosed AML.
This study included 8 patients with MPN-BP and 1 with MPN-accelerated phase (MPN-AP), defined as peripheral or bone marrow blasts of 10% to 19%, which was associated with very high-risk cytogenetics, who were treated at the Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai in New York, New York. Most of the patients in this cohort had relapsed/refractory disease, and had been treated with prior therapies.
A key study finding included the achievement of either a complete response (CR) or a CR associated with incomplete hematologic recovery (CRi) in 3 patients treated with the combination of venetoclax plus decitabine or azacitidine. In addition, stable disease as best response was achieved by 2 additional patients who received this treatment.
Of note, 2 of the 3 patients who achieved a CR/CRi had experienced disease relapse on prior HMA therapy.
“This suggests a synergy with the combination that is not precluded by prior HMA exposure,” the study authors remarked.
Perhaps more striking was the finding that when this therapeutic approach was used as a bridge to HSCT in 3 patients who achieved CR, CRi, or stable disease, all of them were alive at a median follow-up of 8.5 months compared with 4.2 months for the overall cohort.
However, high rates of grade 3 or higher bleeding and infection were observed in this patient cohort, and occurred in 5 and 7 patients, respectively.
“Given the propensity for prolonged cytopenias with resultant complications, caution should be used in patients with baseline cytopenias,” study authors noted.
In closing, the study authors stated, “This is the largest report of venetoclax use in patients with MPN-AP/BP and suggests that this therapeutic strategy is a viable treatment option in this adverse risk group eligible for HSCT.”
They further added that “prospective clinical trial evaluation of combination HMA and venetoclax in MPN-BP is warranted.”
Disclosures: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.
1. Tremblay D, Feld J, Dougherty M, et al. Venetoclax and hypomethylating agent combination therapy in acute myeloid leukemia secondary to a myeloproliferative neoplasm. Leuk Res. Published online September 22, 2020. doi:10.1016/j.leukres.2020.106456
2. U.S. Food and Drug Administration. FDA grants regular approval to venetoclax in combination for untreated acute myeloid leukemia [news release]. U.S. Food and Drug Administration; October 16, 2020. Accessed October 19, 2020. https://www.fda.gov/drugs/drug-approvals-and-databases/fda-grants-regular-approval-venetoclax-combination-untreated-acute-myeloid-leukemia