Efficacy and Safety of Ruxolitinib and Steroids for Treating Patients with Relapsed or Refractory Multiple Myeloma

Introduction

Ruxolitinib (RUX) is an FDA-approved oral, selective inhibitor of Janus kinase (JAK) 1/2 for the treatment of patients with intermediate or high-risk myelofibrosis and polycythemia vera who have had an inadequate response to or are intolerant of hydroxyurea. Preclinical studies from our laboratory have demonstrated that RUX in combination with dexamethasone shows marked anti-myeloma effects both in vitro and in vivo. Specifically, RUX blocks expression of Mucin 1 whose function is linked to lenalidomide (LEN) resistance, downregulates PD-L1 and PD-L2 expression and reduces tumor stimulatory M2 macrophage polarization in multiple myeloma (MM) bone marrow. Recently published results from a Phase 1 trial for 28 heavily previously treated MM patients administered RUX, LEN and methylprednisolone (MP) demonstrated that the therapy was well tolerated and RUX overcame refractoriness to LEN and steroids (Berenson et al., Clin Cancer Res. 2020). The clinical benefit rate (CBR) and overall response rate (ORR) were 46% and 28%, respectively, and all 12 responding patients were refractory to LEN. We evaluated whether the combination of RUX and steroids without LEN was active for treating similar patients through treatment of a cohort within the current trial using this two-drug combination (NCT03110822).

Methods

MM patients must have failed > 3 prior regimens and have been exposed to a proteasome inhibitor and LEN. Patients were treated orally (PO) with 15 mg RUX twice daily on days 1-28 of a 28-day cycle and 40 mg MP every other day. The treatment of this two-drug combination was continued until disease progression (PD). Once PD was confirmed, LEN at 10 mg PO daily on days 1-21 of a 28-day cycle was added to the regimen. Primary endpoints were safety, ORR and CBR.

Results

As of July 15, 2021, 27 patients were enrolled. The median age was 64 years (range, 46-85), and 17 (63%) were male. Patients received a median of 4 (range, 3-11) prior treatments including LEN and steroid-containing regimens to which they were all refractory. Twenty-six patients have completed at least 1 full cycle of therapy; and, thus, were evaluable for efficacy.

The ORR and CBR were 35% (n=9) and 39% (n=10), respectively. Notably, all 10 responding patients were refractory to LEN (i.e., progressed while on or within 8 weeks of last dosage). The remaining patients showed stable disease (n=12) or PD (n=4). The median follow-up was 13 months. The median progression-free survival was 4 months (range, 1-21). The median duration of response was 11 months (range, 1-20). Of 13 patients who progressed on the two-drug combination and had LEN added to their regimen, 6 patients responded (3 MR and 3 PR).

Nine patients experienced SAEs including sepsis (12%), sepsis with neutropenic fever (4%), thrombocytopenia (4%), hyperglycemia (4%), neutropenia (4%), anemia (4%), acute heart failure (4%), rotator cuff tear (4%), osteomyelitis (4%), aspiration pneumonia (4%), pneumonia and pneumothorax (4%), and deep venous thrombosis (4%). Two patients died (one each from pneumonia and PD).

Conclusions

This ongoing Phase 1 trial is the first study demonstrating clinical activity of the two-drug combination of the JAK inhibitor RUX with steroids for MM patients. The treatment was well tolerated and shows promising efficacy for treating heavily previously treated MM patients. Because of this, additional studies are being conducted with higher doses of RUX in combination with MP for this patient population.