Advertisement

Phase I Results of a Multicenter Clinical Trial Combining Guadecitabine, a DNA Methyltransferase Inhibitor, with Atezolizumab, an Immune Checkpoint Inhibitor, in Patients with Relapsed or Refractory Myelodysplastic Syndrome or Chronic Myelomonocytic Leukemia

Casey L. O'Connell, Patricia L. Kropf, Nathan Punwani, Dan Rogers, Richard Sposto and Kirsten Grønbæk

Abstract

Background: There are no FDA-approved therapies for patients with myelodysplastic syndrome (MDS) in whom hypomethylating agents (HMAs) fail, and mechanisms of resistance are not well-characterized. Preclinical and clinical data suggest that some myeloblasts express PDL-1 and that HMAs can induce expression of PD-1 on T cells, which may result in resistance through immune tolerance. We hypothesized that the addition of the PDL1-inhibitor atezolizumab to guadecitabine, a next generation HMA which has a longer in vivo exposure time, would induce or restore HMA sensitivity in patients with relapsed or refractory (R/R) MDS. Overlapping toxicities were not expected given atezolizumab is not myelosuppressive and guadecitabine does not appear to induce autoimmune or inflammatory conditions.

Methods: We are conducting a phase I/II, multicenter clinical trial for adult patients with R/R, intermediate (3+) or high-risk MDS by the revised international scoring system, including chronic myelomonocytic leukemia (CMML). A 3x3 dose escalation design for guadecitabine was used for Phase I, beginning with 30 mg/m2 (Dose level -1) days 1-5 along with a fixed dose of atezolizumab 840mg IV days 8 and 22 of a 28-day cycle. The plan was to escalate to the recommended dose of guadecitabine, 60mg/m2 (Dose Level 1) if no dose limiting toxicities (DLTs) were identified during Dose Level -1. If ≥2/6 DLTs were observed during the Dose Level 1, de-escalation to 45mg/m2 (Dose Level -1.5) would occur. The primary endpoint of phase I was safety and tolerability of the combination. Overall survival (OS) from the on-study date and overall response rates (ORR), based on the 2006 Modified IWG Response Criteria for MDS, were secondary endpoints.

Results: Nine patients (5M, 4F, median age 73) with intermediate or higher risk were treated during phase I. Three patients were treated at Dose Level -1 and sustained no DLTs. Similarly, no DLTs were observed among 6 patients treated at Dose Level 1. There were 17 grade 3 or 4 events considered possibly or probably related to the study treatments, the most common of which were: neutropenia (4), thrombocytopenia (4), and leukopenia (4). The median number of treatment cycles was 5 and the treatment duration for each patient is illustrated in Figure 1. Two patients achieved hematologic improvement (HI) and 1 patient achieved CR. Two patients died after coming off of the study (at 4.5 and 9 months respectively) and the median OS has not been reached.

Discussion: The combination of guadecitabine at the recommended dose of 60mg/m2 D1-D5 along with atezolizumab 840mg IV d8, 22 was found to be safe with an acceptable toxicity profile in patients with R/R MDS. The ORR was 33% and a phase II study is ongoing.

Disclosures Kropf: Celegene: Consultancy; Takeda: Consultancy. Grønbæk: Otsuka Pharma: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Janssen Pharma: Membership on an entity's Board of Directors or advisory committees.

  • * Asterisk with author names denotes non-ASH members.