Vaccine Could Provide Long-Term Acute Myeloid Leukemia Remission

Arjan van de Loosdrecht, MD, PhD

Preliminary findings from an ongoing assessment show an allogenic leukemia-derived dendritic cell vaccine is capable of generating tumor-specific immune responses as well as potential tumor control in patients with acute myeloid leukemia (AML).

The data, presented this weekend at the American Society of Hematology (ASH) 2020 Annual Meeting, also presented 2 incidents in which patients were converted from measurable residual disease (MRD) positive to MRD negative status, with year-plus remission duration, after the vaccination.

International investigators, led by Arjan van de Loosdrecht, MD, PhD, of Amsterdam University Medical Center, are continuing analysis of dendritic cell vaccine candidate DCP-001, for patients with AML. In phase 1 and 2 trial data, the vaccine has shown humoral and cellular immune responses capability as well as conversion of MRD positive patients.

In this current trial presented at ASH 2020, investigators are assessing the vaccine in up to 20 patients with AML who are MRD positive while in first complete remission (CR1). The patients are additionally ineligible for hematopoietic stem cell transplantation (HSCT).

DCP-001 is administered at a primary regimen of 4 times 25.10⁶ or 50.10⁶ cells per vaccination, biweekly, followed by 2 booster vaccinations (10.10⁶ cells per vaccination) at weeks 14 and 18 after start of treatment.

Van de Loosdrecht and colleagues are assessing for a primary endpoint of safety and tolerability for the 2 vaccination schedules and the effect of vaccination on AML patient MRD status. They’re also seeking cellular and humoral immune response associated with DP-001, per peripheral blood assays.

As of July 15 of this year, 10 patients have been enrolled and completed a first dose cohort of 25.10⁶ cells per vaccination. Patient age was 41-76 years old, with gender being split half-male, half-female.

At the time of their reporting, investigators observed consistent tolerance and limited local injection site adverse events. Relapse prior to vaccination schedule completion was observed in 3 patients.

Of the 4 patients eligible for MRD evaluation, 2 became negative at the first timepoint following initial vaccinations at week 14, and remained negative until end of active follow-up, at 32 weeks.

“Two other patients remained in CR, but with MRD positivity,” investigators wrote. “For the remaining 3 patients, to date, no MRD outcome is available yet but patients remain in CR.”

Investigators stressed the small size of patients observed for immune response to DCP-001. However, they also noted one such patient showed a clinical response becoming MRD negative vaccination.

Indeed, they concluded that vaccination with DCP-001 for AML could generate a tumor-specific immune response, and eventually may provide tumor control. Long-term prevention was promising, as the 2 MRD-negative patients remained in complete remission beyond a year after vaccination.

“This study continues to enroll patients at a higher vaccine dose of 50.10⁶ cells per vaccination and additional data on induced immune responses and MRD status will be shown,” investigators concluded.

The study, “Conversion from MRD Positive to Negative Status in AML Patients in CR1 after Treatment with an Allogeneic Leukemia-Derived Dendritic Cell Vaccine,” was presented at ASH 2020.