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

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 and down-regulates 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 and overall response rates were 46% and 28%, respectively, and all 12 responding patients were refractory to LEN. To further evaluate whether RUX and steroids without LEN demonstrate clinical activity and its tolerability in the same patient population, an ongoing Phase I trial was expanded to also include a cohort of patients treated with 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, clinical benefit rate (CBR) and overall response rate (ORR).

Results

As of July 25, 2020, 16 of the planned 29 patients have been enrolled, and 15 patients have completed at least 1 full cycle of therapy; and, thus, were evaluable for efficacy. The median age was 64 years (range, 46‑77), and 9 (60%) were male. Patients received a median of 4 (range, 3-10) prior treatments including LEN and steroids to which they were all refractory.

Of the 15 evaluable patients treated with RUX and steroids, the CBR and ORR were 53% (n=8) and 33% (n=5), respectively. With a median follow-up of 4.7 months, the median duration of response was 3.5 months (range, 1-11+). Five and 2 patients showed stable disease and progressive disease, respectively. Notably, all 8 responding patients were refractory to LEN (i.e. progressed while on or within 8 weeks of last dosage). Of 6 patients who had progressed on the two-drug combination and had LEN added to their regimen, 3 patients responded (2 MR and 1 PR).

Four patients experienced SAEs including sepsis (7%), group B strep sepsis with neutropenic fever and nausea (7%), pneumonia and pneumothorax (7%), thrombocytopenia (7%), and hyperglycemia (7%). Two patients died (one each from pneumonia and progressive disease).

Conclusions

This ongoing phase 1 trial is the first study reporting clinical activity of the JAK inhibitor RUX with steroids for MM. These results demonstrate that RUX with only steroids is also 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.