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 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.
A traditional 3+3 dose escalation design was used to enroll subjects in four cohorts with expansion once a MTD was determined. 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).
Thirty-four patients have been enrolled, and 31 were evaluable for response as of July 13, 2018. The median age was 68 years (range, 49-81), and 20 (59%) were male. Patients received a median of 6 prior treatments including lenalidomide and a PI. No DLTs occurred, and DL+3 was expanded (n=25).
Among all 31 evaluable patients, the CBR and ORR were 48% and 39%, respectively (1 CR, 9 PR, 2 VGPR, and 3 MR), and 11 and 5 showed SD and PD, respectively. Notably, all 15 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 7.4 months. Grade 3/4 adverse events included transient thrombocytopenia (11.1%), anemia (8.8%), neutropenia (6.7%), hypoxia (4.4%) and gastrointestinal bleeding (4.4%). Common serious adverse events included abdominal pain (6.7%), gastrointestinal bleeding (6.7%) and hypoxia (6.7 %).
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 other clinical trials using immunomodulatory agents, steroids and RUX, for treating RRMM patients, and this may represent a new therapeutic approach for these patients.
Berenson:BMS: Consultancy, Honoraria, Speakers Bureau; Amgen: Consultancy, Honoraria; Takeda: Honoraria, Speakers Bureau; Daiichi: Speakers Bureau; Celgene: Honoraria, Speakers Bureau; Janssen: Honoraria, Speakers Bureau.
Asterisk with author names denotes non-ASH members.