Ehab Atallah, MD
This month a couple of studies evaluated the role of enasidenib and gemtuzumab in the therapy of patients with AML using clinical and non-clinical trial data. In a propensity score-matching (PSM) analysis, was enasidenib associated with better outcomes compared to standard of care (SoC). The study included adult patients with relapsed/refractory (R/R) AML with an isocitrate dehydrogenase 2 ( IDH2) mutation ineligible for hematopoietic stem cell transplantation (HSCT) treated with enasidenib (n = 195) from the AG221 C-001 trial or SoC therapies (n = 78) from the French Chart Review study. The SoC regimens included azacytidine, decitabine, cytarabine containing regimens, and others. Enasidenib was associated with superior overall survival (OS) (hazard ratio [HR] 0.67; 95% CI 0.47-0.97) compared to SoC therapies in patients with R/R AML with IDH2 mutation who were ineligible for HSCT. The median OS was 9.26 months vs. 4.76 months for enasidenib and SoC respectively. The results of this study are not surprising given the data seen in clinical trials. Although not evaluated in this study, the quality of life for patients receiving enasidenib is better when compared to SoC regimens, such as 7 +3 (cytarabine + idarubicin). Other than the limitations of a PSM study, which are well acknowledged by the authors, the main weakness is this study did not include venetoclax in the SoC regimen. It remains unclear whether using venetoclax in the R/R setting in patients with IDH2 mutations would lead to similar outcomes.
The benefit of gemtuzumab ozogamicin (GO) was demonstrated again in a metanalysis that included 15 randomized controlled trials and 15 retrospective studies that compared GO (n = 4,768) with non-GO (n = 6,466) therapies in 11,234 patients with AML (n = 11,105) and high-risk myelodysplastic syndrome (MDS) (n = 129). GO showed superior survival outcomes in patients with AML or high-risk MDS than non-GO therapy, but higher doses increased the risk for early death. GO vs. non-GO arm showed improved overall survival (HR 0.86; P = .003), event-free survival (HR 0.86; P = .015), and relapse-free survival (HR 0.83; P = .001). However, GO vs. non-GO was associated with an increased risk for early death at a dose of ≥6 mg/m 2 (relative risk [RR] 2.01; P = .005), hepatic-related adverse effects (RR 1.29; P = .02), and bleeding (RR 1.13; P = .018). Finally, a study by the Polish adult leukemia group demonstrated the safety and efficacy of a low dose cytarabine + cladribine regimen. Treatment consisted of 5 mg/m 2 cladribine intravenously on day 1-5 (in the first cycle) and on days 1 to 3 (in the second cycle) combined with low dose cytarabine (40 mg) subcutaneously once daily on days 1–10. Patients may continue on low dose cytarabine after that if they have achieved at least a partial remission. Rates of overall response and 56-day mortality were 54.0% and 20.5%, respectively. The median overall survival was 6.9 months (95% CI 4.9-9.6) and superior in patients who achieved an objective response (HR 0.04; P < .0001) or partial remission (HR 0.31; P = .0002) compared to nonresponders.
In addition to the better therapies in the last decade, allogeneic hematopoietic stem cell transplantation (allo-HSCT) outcomes have also improved. In a retrospective analysis from the Japanese nationwide transplantation registry the outcomes of patients transplanted with unrelated cord blood (UCB) and Haplo transplant between 2007 to 2014 were worse when compared to patients who had a transplant between 2015 and 2018. For patients who had transplants between 2015 and 2018, the 3-year overall survival of mismatched unrelated donor (MMUD), unrelated cord blood (UCB), and Haplo groups were 60%, 66%, and 63%, respectively ( P = .693). The rates of nonrelapse mortality ( P = .147), relapse ( P = .075), and graft-vs. host disease-free/relapse-free survival ( P = .365) were also similar between the 3 groups. For patients with transplant between 2007 to 2014 the 3 year overall survival was 60%, 54%, and 47% for MMUD, UCB, and Haplo transplants respectively. Newer, better drugs, better tolerated regimens, and improved transplant outcomes were the result: many small gains lead to large improvements.