Prognoses remain extremely poor after hypomethylating agents (HMAs) fail in patients with higher-risk myelodysplastic syndromes (HR-MDS). But a hematologist-oncologist told colleagues that novel therapies are in the works, and some show promise.
Still, “the clinical development for drugs in this setting has been quite challenging, and we have had a lot of drugs that have died in this space over the years,” cautioned Amer Zeidan, MBBS, MHS, an associate professor at Yale University, New Haven, Conn., in a presentation at the virtual Acute Leukemia Forum of Hemedicus. For now, “the best way to manage HMA failure in MDS patients is by preventing HMA failure.”
Dr. Zeidan highlighted a 2016 study – which he led – that found the median overall survival from diagnosis was just a median of 17.0 months (95% confidence interval, 15.8-18.4) in 632 patients with HR-MDS. Another 2016 study, which he also led, reported median overall survival of 11 months (95% CI, 10-14) and 12 months (95% CI, 11-16; P = .26) for patients aged 66 or older who had HR-MDS and took azacitidine and decitabine, respectively. Median survival is even shorter after HMA failure, he said.
The most important obstacle to effective therapy is “the biologic and molecular heterogeneity of the disease,” he said. “Only a certain number of genes are altered in a significant number of patients. And then you have a very long tail, with so many alterations, but most of them are rare. That makes targeting all patients with the same mechanism quite challenging. Also, we poorly understand how hypomethylating agents work and the mechanism of primary and secondary failure. And many MDS patients are older with multiple conditions, multiple comorbidities. By the time of failure, they are generally beaten up and very difficult to enroll in clinical trials.”
Even so, he said, “the understanding of the molecular pathogenesis of MDS is starting to open the door for new drug development opportunities. What’s been changing over the last 5 years is an increased understanding of targeting some of the alterations that are specific to the patient – individualized targeting or precision medicine.”
Novel therapies
Dr. Zeidan said the novel therapies for HR-MDS after HMA failure fall into these categories: molecularly targeted agents, genetically agnostic small-molecule inhibitors, immunotherapies, and chemotherapy/epigenetic agents.
Multiple trials, for example, are examining a chemotherapy treatment CPX-351 (liposomal cytarabine-daunorubicin) in HR-MDS, and a 2018 study showed improvement in median survival in older patients with newly diagnosed secondary acute myeloid leukemia. “However, this remains an investigational treatment,” Dr. Zeidan cautioned.
Venetoclax is also being studied. Animal and cell culture data suggest there may be helpful synergistic activity between venetoclax and azacitidine in both the frontline and relapse settings. Dr. Zeidan highlighted his own 2019 report on a phase 1b study of venetoclax versus venetoclax and azacitidine in the HMA failure/HR-MDS setting. The results are “quite exciting,” he said.
The report noted that, “although the study is still ongoing, the 6-month OS [overall survival] estimate of 57% in monotherapy [patients] compares favorably to historical controls.”
Glasdegib is “another drug of interest,” although it’s mostly been studied in the frontline setting, he said, and “we don’t have much data with this drug in the refractory setting for MDS patients.” APR-246 is also intriguing, he said, but again lacks data in the refractory setting.
Dr. Zeidan noted research into other treatments – rigosertib (recent findings have been disappointing), ivosidenib for IDH1-mutated MDS, AG221-001 and enasidenib (targeting IDH2 mutations), trametinib (targeting RAS pathway mutations), and others. For now, “clinical trial participation should be the best way to manage these patients.”
Dr. Zeidan disclosed multiple disclosures, including relationships with Pfizer, Novartis, Abbvie, Pfizer, Medimmune/AstraZeneca and Boehringer Ingelheim, among others.
The Acute Leukemia Forum is held by Hemedicus, which is owned by the same company as this news organization.