Phase II Trial of SGI-110 (Guadecitabine) in Philadelphia Negative Myeloproliferative Neoplasms

Introduction:

Philadelphia negative myeloproliferative neoplasms (Ph- MPN) are hematopoietic stem cell malignancies associated with poor median survival of 12.4 months. They are often excluded from clinical trials because there are no accepted standards for treatment or assessment of disease response. SGI-110 (guadecitabine) is a second-generation DNA hypomethylating agent (HMA) that is currently in clinical trials for the treatment of myelodysplastic syndrome and acute myeloid leukemia. Guadecitabine was designed to resist degradation by protein aminases and prolong the exposure of tumor cells to the active metabolite decitabine. The purpose of this study was to test the efficacy and safety of SGI-110 in Philadelphia chromosome negative MPNs (Ph- MPN) and to also test the clinical applicability of the International IWG MDS/MPN response criteria in a prospective trial¹.

Methods:

This is an interim analysis of an open label single-arm, single-institution study to evaluate the efficacy and safety of SGI-110 in Philadelphia chromosome negative (Ph-) myeloproliferative Neoplasms as classified by WHO, including chronic neutrophilic leukemia (CNL), atypical chronic myeloid leukemia (aCML), chronic myelomonocytic leukemia (CMML), myelodysplastic/myeloproliferative neoplasm unclassifiable, accelerated phase myelofibrosis and MPN unclassifiable (defined as peripheral and or bone marrow blasts of 10-19%). PV, ET and primary/secondary myelofibrosis were excluded. Patients were required to complete at least 3 cycles of guadecitabine to be considered evaluable for efficacy. Safety analyses were done on all patients who received any treatment with guadecitabine. Guadecitabine was administered subcutaneously at a dose of 60mg/m² on days 1-5 repeated every 28 days. The IWG MDS/MPN response classification was used to assess treatment response.

Results:

Baseline characteristics of the study participants are presented in Table 1. Among the 20 treated patients, 2 (10.0%) were treated with previous HMAs, 3 had progressive disease, 1 transferred care, 7 were not yet evaluable for response, and 1 died after receiving only 2 cycles of treatment. Of the 13 evaluable, protocol specific response was seen in 8 (61.5%) patients: 2 (15.4%) achieved complete remission (CR), 3 (23.1%) with optimal marrow response (OMR), 3 (23.1%) with hematological response/clinical benefit (CB). Stable disease was seen in 4 patients (30.8%). Of the 7 patients that were inevaluable: 3 had progressive disease before completing 3 cycles, 2 received <3 cycles of therapy, 1 discontinued treatment due to personal choice, and 1 patient died from infection after receiving 2 cycles of treatment.

The median overall survival (OS) for all evaluable patients was 27.4 months with 25.8 months for responders. Median OS for patients who achieved CR was 27.4 months and 25.0 months for OMR. For patients with CB, mean survival was 21.0 months. There was 1 patient with stable disease with prolonged survival (21 cycles), which elevated the mean survival to 26.0 months for the SD category. The median number of cycles to achieve a response was 3. The median times to first and best response were 3.6 and 3.8 months, respectively. The combination of ASXL1 and EZH2 mutations was associated with rapid progression.

The most common AEs and SAEs related to guadecitabine are listed in Tables 2 and 3 respectively.

Conclusion: SGI-110 was safe and well tolerated in patients with Ph negative MPN, with encouraging efficacy in this difficult-to-treat patient population. Further investigation of this agent in MDS/MPN overlap syndromes is warranted, and the present trial is ongoing.

1. Savona MR, Malcovati L, Komrokji R, et al. An international consortium proposal of uniform response criteria for myelodysplastic/myeloproliferative neoplasms (MDS/MPN) in adults. Blood. Mar 19 2015;125(12):1857-1865.

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