A Phase 1 Trial of Ruxolitinib, Lenalidomide and Methylprednisolone for Patients with Relapsed/Refractory Multiple Myeloma (MM)

Introduction

Ruxolitinib (RUX) is an FDA-approved oral, selective inhibitor of Janus kinase (JAK) 1/2 for the treatment of patients with polycythemia vera who have had an inadequate response to or are intolerant of hydroxyurea or intermediate or high-risk myelofibrosis (MF). Preclinical studies from our laboratory have demonstrated that RUX in combination with the immunomodulatory agent lenalidomide (LEN) and dexamethasone shows marked anti-myeloma effects both in vitro and in vivo. Furthermore, MUC1 (Mucin 1) is responsible for LEN resistance in MM cells, and RUX blocks its expression in multiple myeloma (MM) cells. Thus, RUX may restore sensitivity to LEN. RUX also downregulates PD-L1 and PD-L2 expression on MM cells and reduces tumor stimulatory M2 macrophage polarization in MM bone marrow. Therefore, a phase 1 trial was conducted to determine the safety and efficacy of RUX in combination with LEN and the steroid methylprednisolone (MP) for relapsed/refractory (RR) MM patients who had previously been treated with LEN/steroids and a proteasome inhibitor (PI) and showed progressive disease at study entry.

Methods

A traditional 3+3 dose escalation design was used to enroll subjects in four cohorts with planned total enrollment to be 49 patients. Subjects received RUX twice daily continuously, LEN daily on d1-21 of a 28-d cycle and MP orally every other day. In DL0, patients received RUX 5 mg, LEN 5 mg, and MP 40 mg. In DL+1 and +2, both doses of LEN and MP remained unchanged and RUX was escalated to 10 and 15 mg, respectively. DL+3 escalated LEN to 10 mg with MP unchanged and RUX at 15 mg. Primary endpoints were safety, clinical benefit rate (CBR) and overall response rate (ORR).

Results

As of March 1, 2019, 43 patients were enrolled, and 40 were evaluable for efficacy. The median age was 65 years (range, 46-81), and 25 (58%) were male. Patients received a median of 6 prior treatments including LEN and steroids to which they were all refractory. No DLTs occurred, and DL+3 was expanded.

Among all 40 evaluable patients, the CBR and ORR were 47% and 37%, respectively (1 CR, 4 VGPR, 10 PR and 4 MR), and 16 and 5 patients showed SD and PD. Notably, all 19 patients achieving > MR were refractory to LEN (i.e. progressed while on or within 8 weeks of last dosage). The median PFS for all evaluable patients was 4 months. G3/4 AEs included anemia (16%), sepsis (14%), lymphocytopenia (14%), pneumonia (12%), neutropenia (12%) and hypokalaemia (12%). Most common SAEs included sepsis (14%) and pneumonia (12%).

Conclusions

This phase 1 trial demonstrates for the first time that a JAK inhibitor, RUX, can overcome refractoriness to LEN and steroids for RRMM patients. This all oral regimen was well tolerated, and reversible Grade 3/4 cytopenias occurred in only a small minority of patients. These promising results are leading to expansion of the current clinical trial to 78 patients, and represent a potential novel therapeutic approach for treating MM.