A Phase II Study of CPX-351 As a Novel Therapeutic Approach for Patients with Myelodysplastic Syndromes (MDS) after Hypomethylating Agent Failure

Treatment options are limited for patients (pts) diagnosed with MDS at the time of hypomethylating agent (HMA) failure. One goal is to introduce another line of therapy to reduce tumor burden and enable patients to undergo hematopoietic stem cell transplant (HSCT), which may prolong survival for a subset. CPX-351, has shown better overall response rates and improved overall survival in patients with acute myeloid leukemia with underlying MDS changes compared to 7+3, suggesting that CPX-351 can be used in an MDS patient population. We hypothesized that treating MDS pts, who were failed by HMAs or were intolerant with CPX-351 would overcome HMA resistance.

This is a phase II study of single agent CPX-351 administered at the standard FDA approved dose of 44 mg/m2 (daunorubicin 44 mg/m2 and cytarabine 100 mg/m2) intravenously on days 1, 3, 5 of the induction cycle. If patients achieve complete remission (CR), marrow CR, partial remission or hematologic improvement per 2006 IWG criteria they will be eligible to continue on to consolidation therapy, which consists of CPX-351 at a dose of 15.4 mg/m2 (daunorubicin 15.4 mg/m2 and cytarabine 35 mg/m2) every 28 days. Pts can receive up to 4 cycles of consolidation therapy in the absence of toxicity.

The primary objective of the trial is to evaluate the efficacy of CPX-351 as measured by overall response rate (ORR) by IWG 2006 criteria. Secondary objectives include: ,1) determine the time to response (TTR), 2) evaluate the duration of response (DOR), 3) evaluate the event-free survival and the overall survival probability during trial period. Pts are risk stratified into lower vs higher-risk prior to enrollment using the Post-HMA model (Nazha A, et al. Hematologica 2016). Eligibility includes: pts >18 years with primary or secondary resistance to HMA, ECOG performance status < 2 and adequate organ function. Pts are excluded if they have uncontrolled infection or active malignancy. A total of 18 pts will be enrolled to each arm (lower and higher risk).

To date, three pts were enrolled. One with MDS refractory to HMA who achieved complete remission and proceeded with 4 cycles of consolidation. The pt remained in remission 6+ months after the completion of consolidation. Another patient achieved a marrow CR but had a fungal pneumonia and then was taken off the trial (patient choice for going to hospice). The third patient had MDS/MPN, completed induction and achieved stable disease with improvement in platelets and neutrophils. All patients were lower-risk per the stratification model. No unexpected toxicity was observed.

In conclusion, preliminarily CPX-351 is effective in MDS patients after HMA failure who are eligible to receive intensive chemotherapy. The treatment was well tolerated and toxicities were similar to what was observed in pivotal CPX-351 trials. The trial is ongoing and the results will be updated in the meeting.