Ixazomib and Daratumumab without Dexamethasone (I-Dara) in Elderly Frail RRMM Patients. a Multicenter Phase 2 Study (IFM 2018-02) of the Intergroupe Francophone Du Myélome (IFM)

Purpose: Frail patients with multiple myeloma have an inferior outcome, especially in the relapse setting. This adverse prognosis is mainly related to a high discontinuation rate due to treatment related adverse events. The aim of this phase 2 study is to evaluate efficacy and tolerability of Ixazomib-Daratumumab (I-Dara) without Dexamethasone in elderly frail patients with relapsed myeloma (NCT03757221).

Methods: Fifty Ixa-Dara naïve RRMM patients (1-2 prior therapy) were planned to receive oral Ixa (4 mg: days 1, 8, 15), IV Dara (16 mg/kg; days 1, 8, 15, 22, cycles 1-2; days 1, 15, cycles 3-6; days 1, cycles 7+) and IV Methylprednisolone before Dara (100 mg at day 1, 8, cycle 1 and then 60 mg). They were enrolled if frailty score was ≥2 by IMWG score and FIRST proxy score (Facon T et al, Leukemia, 2020). The primary endpoint was ≥very good partial response rate at one year. Secondary endpoints included ORR, PFS, OS & toxicity according to NCI-CTCAE version 5.0.

Results: Among 52 patients screened during this ongoing trial, 44 were included between 03/2018 and 05/2021. Patient were at first (n=28) or second relapse (n=16). Thirty -eight patients (86%) were previously exposed to bortezomib and 8 (18%) were previously refractory to lenalidomide. Median age was 82 (80-84). All patients had a frailty score ≥2. In 22 patients ISS was stage I (n=5), II (n=10) or III (n=7). Eleven (32%) patients harbored high-risk cytogenetic, including t(4;14) (n=3) or del17p (n=8). The median duration of Tx among 23 pts with ongoing Tx was 6 months [0-27] at data cutoff (July 19)]. The median duration of Tx among 21 pts who stopped Tx was 7 months [0-21]: 13 had progressive disease. Six patients died during the study: Daratumumab-related bronchospasm (D1C1); Ixazomib-related overdose (C2); progressive disease (C2 & C4), sepsis (C1 & C2). Regarding toxicity, 28 ≥grade 3 AE occurred amongst 24 pts (54%). The most common grade 3-4 toxicities were thrombocytopenia (n=5), other cytopenias (n=4), infection (n=4) and gastrointestinal disorders (n=2). Fourteen out of 28 were SAE including 1 bronchospasm, 1 acute respiratory failure and 2 ixazomib overdoses. Overall response rate, including minimal response, was 86 % in pts with ongoing treatment and 71% in pts who stopped Tx; ≥VGPR rate was 33% and 6% respectively.

Conclusions: These preliminary results show a favorable safety profile of ixazomib and daratumumab combination, without dexamethasone, in this specific population of very elderly frail patients with RRMM and high risk cytogenetic for almost one third of them. Efficacy results will be analyzed when the 50 patients will be enrolled in the study and evaluable for the primary endpoint.