First Interim Results of a Phase I/II Study of Lenalidomide in Combination with Anti-PD-1 Monoclonal Antibody MDV9300 (CT-011) in Patients with Relapsed/Refractory Multiple Myeloma

Introduction: Multiple myeloma (MM) is associated with profound and widespread disarray of both the adaptive and innate arms of the immune system including loss of effector T cell function, humoral immune deficiency, and natural killer (NK) cell immunity.  This immunosuppressive milieu is crucial to promoting disease progression. Standard treatment options (immunomodulators (IMIDs) and proteosome inhibitors, radiation, and high-dose corticosteroids) offer modest benefit, but also contribute to further immune suppression.  Little is known regarding the mechanisms by which immune dysfunction and immunoevasion occur. Our group has characterized an important role for the programmed death receptor-1 (PD-1) / PD-L1 signaling axis in these processes. MDV9300 (formerly CT-011 / Pidilizumab) is a novel IgG1 humanized monoclonal antibody (mAb) that modulates the immune response through interaction with PD-1.  Lenalidomide (Len) an IMID exerts efficacy in MM in part through enhancement of NK cell versus MM effect - an effect likely mediated through T cell production of interleukin (IL)-2. In our in-vitro study, pretreatment of NK cells with MDV9300 with or without Len enhanced immune complex formation between NK cells and MM tumor targets and also augmented NK cell activation and cytotoxicity against MM.  We sought to determine the safety, tolerability and any early signs of efficacy in relapsed or refractory MM patients using MDV9300 in combination with Len. 

Methods: In the phase I portion, the primary endpoint is to determine the maximum tolerated dose (MTD) of the combination. Key eligibility criteria are relapsed or refractory disease but not progressed on Len 25 mg; ≥2 prior lines of therapy, absolute neutrophil count ≥ 1000/µL; Platelets ≥60,000/µL; and creatinine clearance of ≥ 40ml/min. Patients are treated with escalating doses of MDV9300 and Len utilizing a 3x3 escalation design (Table 1). If stable disease is the best response after 4 cycles, patients have the option of adding dexamethasone (20-40mg weekly). Len dose may be modified independently of MDV9300.  Patients can receive a maximum of 12 cycles of therapy. 

Results: Twelve patients are evaluable to date. The median age was 68.5 (range 49–82) and the median time from diagnosis 4.98 years (range 1.54–12.62). At study entry, 67% had high risk cytogenetics (del 17p, complex karyotype, gain 1q) and the median number of prior treatment lines was 2 (range 2-11). 100% of patients had received prior Len, bortezomib and Dex, 50% alkylating agents (cyclophosphamide, oral melphalan, bendamustine), 75% autologous stem cell transplant, 25% pomalidomide and 33% carfilzomib. MDV9300 infusion has been well tolerated with only one grade 2 infusion related toxicity with sore throat. The patient received hydrocortisone with no further reaction observed. Grade 3/4 Anemia, neutropenia, and thrombocytopenia attributable to therapy have been seen in 25%, 23%, and 34% of patients, respectively. Other common grade 2-3 therapy related adverse events are fatigue (50%), anorexia (17%), and hypophosphatemia (17%). There has been no grade 3 or higher infection and no worsening of neuropathy from baseline. Len dose was reduced in 3 patients (25%) and increased in one. There has been no dose reduction in MDV9300. Dex 20 mg or less was added in 2 patients for muscle cramps and < PR after 3 cycles.  To date 7 patients are off therapy; 1 due to grade 3 fatigue and 6 due to disease progression. Five patients continue on therapy at respective 12, 11, 9, 5 and 3 months. Responses to date have been 3 Very good partial response,1 partial response, 2 minimal response and 2 stable disease.

Conclusion:  The combination of steroid sparing MDV9300 and Len regimen has demonstrated an acceptable toxicity profile to date with evidence of anti-myeloma activity. This is the first reported combination anti-PD-1 based immune therapy for MM.  Updated results will be presented at the meeting including the MTD dose for phase II.

Table 1

	MDV9300- mg/kg Intravenously given on day 3 every 28 days	Lenalidomide- mg orally days 1-21 every 28 days	DLT Evaluable	DLTs
Cohort 1	1.5	15	6	Grade 3 fatigue. Cohort extended to 6
Cohort 2	3	15	3	none
Cohort 3	3	25	3	none
Cohort 4	6	25	0

Acknowledgements: Drug has been provided by Medivation; The study is sponsored by the American Cancer Society