Abstract

Background: HMA therapy is standard of care for patients with MDS. Outcome post HMA failure is poor with a median survival of 4-6 months. Clofarabine is a second generation nucleoside analog with single agent activity in MDS. The objective of this phase II trial is to evaluate the safety and activity of the combination of clofarabine and low dose cytarabine in the treatment of patients with high risk MDS who failed prior HMA therapy.

Methods: Eligible patients were adults older than 18 years with MDS intermediate-1 and higher by the IPSS, who have had no response, progressed, or relapsed following at least 4 cycles of therapy with either azacitidine and/or decitabine. Patients were required to have an Eastern Cooperative Oncology Group performance status of </=2 at the time of study entry. Responses were defined according to International Working Group 2006 criteria. Induction therapy consisted of clofarabine 10-15 mg/m2 IV daily X 5 days (days 1-5) and cytarabine 20 mg SC twice daily X 7 days (days 1-7). Patients could receive up to 3 induction cycles as long as they tolerated the therapy and had stable disease. Responding patients proceeded with consolidation therapy with clofarabine 10-15 mg/m2IV daily X 3 days (days 1-3) and cytarabine 20 mg SC twice daily X 5 days (days 1-5) for a maximum of 12 cycles. Cycles were repeated every 4 to 8 weeks depending on hematopoietic recovery and resolution of toxicities.

Results: From January 2012 to August 2015, 80 eligible patients were enrolled in this prospective study (NCT01444742) and received a median of 2 cycles (range, 1-12) (Table 1). The overall response rate (ORR) was 46% (16 [20%] achieved complete remission (CR), 17 [21%] marrow CR, 1 [1%] partial response (PR), 3 [4%] hematological improvement (HI)) with a median response duration of 7 months. The median time to response was 42 days (range, 9-191). By multivariate analysis, complex karyotype was the only independent factor predicting for response (hazard ratio [HR] 0.13; 95% confidence interval [CI]: 0.03- 0.62; p=0.01). Of the 37 patients with diploid karyotype, the overall response was 68% (7 [19%] achieved CR, 15 [41%] marrow CR, 1 [3%] PR, 3 [4%] HI). Nine of the responding patients received subsequent allogeneic stem cell transplant (ASCT). With a median follow-up of 24 months (range: 1-51 months), the median event-free survival (EFS) and overall survival (OS) times were 5 months (95% CI: 2.7-6.3) and 11 months (95% CI: 6.5-14.9), respectively (Figure 1). The median OS for responding and non-responding patients was 24 months (95% CI: 11.7-35.6) and 5 months (95% CI: 2.8-6.2), respectively (p<0.001). There was no difference in OS whether patients were censored or not at the time of ASCT (p=0.463). At last follow-up, 22 patients (28%) remained alive: 1 is receiving low-dose clofarabine and cytarabine, 5 are alive in response after ASCT, 9 are receiving salvage therapy, 1 went to hospice, and 6 were lost to follow-up. By multivariate analyses, complex karyotype, platelet count less than 30 x 109/L, and poor performance status were independently associated with poor survival. In addition, the response to the combination of low-dose clofarabine and cytarabine was independently associated with better OS (HR 0.17; 95% CI 0.09-0.36; p<0.001). Grade ≥ 3 therapy-related toxicity included infections (34%), increased liver functional tests (8%), acute renal failure (3%), skin rash (3%), syncope (1%), and rectal bleeding (1%). Twenty-two (28%) patients had clofarabine dose reduction after a median of 2 courses. After 47 patients were enrolled and several patients experienced infections during induction, the protocol was amended to reduce the dose of clofarabine to 10 mg/m2 per day for 5 and 3 days during the induction and consolidation phases, respectively. There was no difference in responses before and after the modification to the protocol's dosing schedule (p=0.314).

Conclusion: The combination of low-dose clofarabine and cytarabine in patients with higher-risk MDS after HMA failure resulted in an ORR of 46% and median OS of 11 months and may be particularly effective in patients with diploid karyotype. Our results also indicate that the combination of low-dose clofarabine and cytarabine may be useful as a bridge to ASCT in eligible patients.

Disclosures

Jabbour:ARIAD: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Novartis: Research Funding; BMS: Consultancy. Cortes:ARIAD: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Teva: Research Funding. Jain:Abbvie: Research Funding; Infinity: Research Funding; Servier: Consultancy, Honoraria; Incyte: Research Funding; Genentech: Research Funding; Pharmacyclics: Consultancy, Honoraria, Research Funding; ADC Therapeutics: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria, Research Funding; Celgene: Research Funding; Seattle Genetics: Research Funding; Novimmune: Consultancy, Honoraria; BMS: Research Funding. DiNardo:Agios: Other: advisory board, Research Funding; Daiichi Sankyo: Other: advisory board, Research Funding; Novartis: Other: advisory board, Research Funding; Abbvie: Research Funding; Celgene: Research Funding. Konopleva:Cellectis: Research Funding; Calithera: Research Funding.

Author notes

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Asterisk with author names denotes non-ASH members.

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