Descriptive Analysis of Isatuximab Use Following Prior Daratumumab in Patients with Relapsed/Refractory Multiple Myeloma

Background: Anti-CD38 monoclonal antibodies (mAb) like daratumumab (dara) have become integral in managing relapsed/refractory (RR) and newly diagnosed (ND) multiple myeloma (MM). Isatuximab (isa), a newer CD38 mAb, induces direct rather than indirect apoptosis of MM cells. However, little is known about whether the use of one prior CD38 mAb will alter the efficacy of another in subsequent lines of therapy.

Methods: All patients (pts) with MM treated at MD Anderson with isa after receiving dara in prior lines of therapy were identified. We conducted a retrospective analysis with data points including patient and disease characteristics, responses to dara, response to isa, the presence of high risk features, and the presence of t(11,14).

Results: 9 pts were identified, ages 56-72. 5 pts (55%) were male. 5 pts (55%) were alive at the time of data cutoff. 5 pts were Hispanic, 3 White, and 1 Black. 8 pts (89%) had high risk features as represented by the presence of del17p, t(4,14), t(14,16), t(14,20), p53 mutations, gain 1q, extramedullary disease (EMD), CNS disease, early relapse (within 1 year) after autologous transplant, or an increased (>5%) peripheral blood plasma cells (PBPC). 2 (22%) had t(11,14). 4 (44%) had IgG MM. 2 (22%) with light chain disease, 2 (22%) with IgA MM, and 1 (11%) with IgD MM. Dara was initially used in lines 2-7. Dara combinations with pomalidomide (pom), bortezomib (bor), thalidomide (thal), lenalidomide (len), or carfilzomib (car); and pom combinations that also included elotuzumab (elo) or Cytoxan (cytox) are noted in table 1. Dara was discontinued (dc’d) in 8 pts due to progressive disease (PD) and in 1 pt due to toxicity. 8 pts (89%) experienced a best overall response (ORR) of partial response (PR) to dara; 1 pt had stable disease (SD). All pts received prior len and 8 pts received prior pom at some time during the treatment of MM. All pts received isa in combination with pom/dexamethasone (dex). Best ORR to isa/pom/dex: 5 pt (55%) had PR, 2 pt with minimal response (MR), 1 SD, 1 PD. Median treatment duration of isa/pom/dex was 5 weeks (2-14 weeks) at data cutoff. 3 pts dc’d isa/pom/dex due to infections, and 2 due to later progression. 2 pts remain on therapy. 1 pt chose to dc all MM therapy for quality of life purposes despite PR with isa/pom/dex. 1 pt died from cardiac disease unrelated to MM or treatment.

Conclusions: Our current study of heavily pretreated pts with RRMM demonstrates that despite prior anti-CD38 therapy with dara, most patients (77%) experienced a response of MR or better with treatment with another anti-CD38 therapy isa. To our knowledge, this is the first report of outcomes to isa in patients with prior dara therapy. Further long term follow up will be needed to determine the length of response. Additional studies are planned to further evaluate this patient population.