CPX 351 As First Line Treatment in Higher Risk MDS. a Phase II Trial By the GFM

Background and aims: intensive chemotherapy (IC) has been used since the early 90's in the treatment of higher risk MDS, yielding 40 to 50% complete response (CR) but prolonged myelosuppression and 10 to 30% early deaths. IC is also recommended before allogeneic (allo) SCT when marrow blasts are increased (De Witte et al, Blood, 2017). CPX-351, a liposomal combination of cytarabine and daunorubicin, proved greater efficacy than classical IC with 3+7 in secondary-AML, including in patients with 20-30% marrow blasts and those who subsequently received allo SCT (Lancet et al, Lancet Haematol, 2021). We evaluated response to CPX-351 in a group of untreated higher risk MDS patients, most of whom were candidates for allo SCT.

Methods: This prospective study, involving 12 GFM centers, included int-2 or high IPSS MDS, previously untreated with HMA or chemotherapy, and aged <70 years. CPX-351 induction treatment was given at 44mg/m ² (DNR)/ 100mg/m ² (CYT)/ day on days 1, 3 and 5. A second induction cycle (same daily dose, days 1 and 3 only) was allowed in patients who failed to achieve at least partial response (PR) according to IWG 2006. Consolidation cycles (same daily dose for one day) were planned (4 cycles) in responders. Allo SCT could follow after 1 to 4 consolidation cycles. Response to induction treatment, evaluated per protocol between day 28 and day 42, often had to be delayed due to prolonged cytopenia. For response evaluation, ELN 2017 criteria for AML were used in addition to IWG 2006 criteria for MDS, as the latter often proved difficult to interpret in the presence of persisting moderate cytopenia (especially the requirement of a Hb level ≥ 11 g/dl for CR definition).

Results: 31 patients were included between July 2020 and January 2021. Median age was 62 years (range 31-69); WHO classification: 26 MDS-EB2, 5 CMML-2; IPSS: int-2: 84%, high: 16%; R-IPSS: intermediate: 29%, high: 55%, very high: 16%; karyotype: 2 very good, 22 good, 3 intermediate, 2 poor, 2 very poor. 27 patients received one induction cycle and 4 (in stable disease (SD) after the first cycle), a second induction cycle. Response rates, eventually evaluated a median of 53 days (range 28-112) from onset of induction, were with ELN 2017 criteria: CR: 52%, CRi: 13%, MLFS: 23%, SD: 13% and with IWG 2006 criteria : CR: 23%, mCR: 45%, mCR + HI-P: 6%, mCR + HI-P + HI-N: 6%, mCR + HI-N: 3%, PR: 3%, SD: 13%. Minimal residual disease assessment by NGS and flow cytometry will be presented at the meeting. 24/27 patients with baseline marrow blasts >10%, reached <5% blasts after induction treatment (figure 1). Median time to platelets >20G/L and >50G/L were: 16 (range 0-55) days and 28 (range 8-51), respectively and to ANC >1G/L: 26 (range 2-60) days. Only one patient had grade ≥ 3 mucositis and 4 had grade ≥ 2 alopecia during induction treatment. No patient died during induction treatment or required management in the intensive care unit.

With a median follow-up of 201 days (range 102-350), 22 of the 30 patients initially considered for allo SCT received transplant after no (10 pts), 1 (9 pts), 2 or 3 (3 pts) consolidation cycles and 5 are planned for allo SCT. Reasons for not being transplanted were, investigators' choice (n=1), relapse (1), no donor (1) and invasive fungal infection (n=1). None of the 4 non transplanted patients received consolidation cycles. Reasons for not receiving consolidation cycles were persistent cytopenia (n=5), cardiac toxicity (n=2), failure to achieve CR or PR (n=2). At the time of analysis (June 2021), 4 patients had relapsed, after 3 to 6 months of response.

Conclusions : CPX-351 is effective in higher risk MDS/CMML, especially to achieve blast clearance, and as a bridge to allo SCT.

Figure 1: waterfall plot according to IWG 2006 and ELN 2017 criteria

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