Outcomes of anti-CD38 isatuximab plus pomalidomide and dexamethasone in five relapsed myeloma patients with prior exposure to anti-C38 daratumumab: case series.

Daratumumab is the first anti-CD38 monoclonal antibody (Mab) used to treat myeloma in the newly diagnosed setting and in the relapsed setting. Isatuximab, another Mab targeting a specific epitope on the CD38 receptor, was recently approved in the UK in combination with pomalidomide and dexamethasone (IsaPomDex) to treat myeloma patients who received three prior lines of therapy. However, there is a lack of understanding of whether using a prior anti-CD38 Mab (e.g. daratumumab) can affect the efficacy of another Mab (e.g. isatuximab), when the latter is used to treat a subsequent relapse. We performed a UK-wide outcomes study of IsaPomDex in the real-world. In this case series, we report a detailed descriptive analysis of the characteristics and clinical outcomes of five IsaPomDex patients in UK routine practice (Patients I to V), with a prior exposure to daratumumab. Age range was 51-77 years with two patients >70 and three patients <70 years. The cytogenetic risk was standard in two patients, high in two patients and not known in one patient. Prior daratumumab regimen were monotherapy (dara-mono) in one patient (II), and daratumumab with bortezomib and dexamethasone (DVd) in four patients. Responses to prior daratumumab were: very good partial response (VGPR) in two patients (I and III), minor response-stable disease (MR-SD) in one patient (II), and progressive disease (PD) in two patients (IV and V). Median (range) number of IsaPomDex cycles received was 2 (1-4). Outcomes of IsaPomDex were PD in three patients (II, IV and V) and a response in two patients. Response categories were: MR-SD in patient I and PR in patient III. Despite the limitations of our case series, we described the first UK real-world report of IsaPomDex outcomes in myeloma patients with a prior exposure to daratumumab. Large prospective studies are required to further evaluate myeloma outcomes in this setting.