Several recently approved and late-phase investigational agents may improve care for patients with higher risk myelodysplastic syndrome (MDS) by augmenting hypomethylating agents (HMAs), which are the current standard of care.
“HMA failure remains a challenge, and new approaches, such as ex vivo drug screening, are needed to improve outcomes,” said Brian A. Jonas, MD, PhD, from the University of California, Davis, in an online presentation during the virtual American Society of Hematology (ASH) Meeting on Hematologic Malignancies.
The goal of treatment for patients with higher-risk MDS – defined as a Revised International Prognostic Scoring System (R-IPSS) intermediate, high-risk, or very high–risk category – is to alter as much as possible the natural history of the disease.
Treatment options include monotherapy with HMAs, HMAs in combination with other agents, high-intensity chemotherapy, allogeneic hematopoietic stem cell transplant (allo-HSCT), or a clinical trial, Dr. Jonas said.
Improving bioavailability
Although HMAs, either azacitidine or decitabine, remain the standard of care for patients with higher-risk MDS, the oral bioavailability of these agents is limited by the rapid clearance of cytidine deaminase in the gut and liver.
But as Savona and colleagues reported in The Lancet Haematology, the combination of oral decitabine with cedazuridine, a novel cytidine deaminase inhibitor, significantly improved the bioavailability of the HMA, with an efficacy comparable to that of intravenous decitabine. The findings were confirmed by results from the phase 2 ASCERTAIN trial.
The combination (Inqovi) was approved by the US Food and Drug Administration in July 2020 for the treatment of MDS and chronic myelomonocytic leukemia in IPSS intermediate-1 or higher risk categories. The approved dose is 35 mg decitabine and 100 mg cedazuridine in a single oral tablet once daily on days 1 through 5 of each 28-day cycle.
New drugs, potential new targets
Another promising approach to improving HMA therapy is the combination of azacitidine and the BCL-2 inhibitor venetoclax (Venclexta).
Results of a phase 1b study of the combination as first-line therapy for patients with higher-risk MDS showed a combined complete response and marrow complete response rate of 77.2%, with estimated 6-month and 12-month survival rates of 100% and 93.8%, respectively, for patients who had a complete response and 85.9% at both 6 and 12 months for patients with a marrow complete response.
“The question is does this challenge the standard of care for higher-risk MDS? I would argue that many are using the regimen since the abstract came out, and I myself consider this regimen for use in select patients with high–blast count MDS who are maybe going to transplant or need to have their disease controlled rapidly,” Dr. Jonas said.
A randomized trial of the combination (NCT04401748) is currently recruiting.
Novel checkpoint inhibitor
Another promising combination pairs azacitidine with magrolimab, an experimental immune checkpoint inhibitor that targets CD47, the “don’t eat me” signal that inhibits macrophages from carrying out their crucial phagocytosis role.
As previously reported, magrolimab in combination with rituximab showed good efficacy in patients with relapsed or refractory indolent or aggressive non-Hodgkin lymphomas, and more recently showed promise in combination with azacitidine in a phase 1b study for the treatment of MDS and acute myeloid leukemia (AML).
Among patients with MDS in the trial, the overall response rate was 91% (30 of 33 patients). In all, 14 patients had complete responses, one had a partial response, eight had marrow complete responses, and seven had hematologic improvement.
The tolerability profile was similar to that seen with azacitidine monotherapy, with no significant worsening of cytopenias or infections or autoimmune adverse events. There were no deaths in the first 60 days on therapy, and no treatment discontinuation for drug-related adverse events.
Azacitidine was paired with a different novel agent, APR-246 in a clinical trial testing the combination in patients with TP53 mutant MDS and AML. APR-246 is a novel, first-in-class small molecule that binds covalently to p53, and selectively induces apoptosis in metastatic TP53 cells via thermodynamically stabilizing the p53 protein and shifting equilibrium toward the wild-type conformation.
Among 33 evaluable patients with higher-risk MDS, the combination was associated with an overall response in 29 (81%) including 20 patients (61%) with a complete response. After a median follow-up of 10.8 months, the median duration of response was 7.3 months, and 17 patients went on to allo-HSCT.
The combination of magrolimab and azacitidine has also shown preliminary activity in TP53-mutated MDS, Dr. Jonas noted.