Abstract. We set out to generate new human myeloma tumors that grow in immunodeficient mice and can be used for pathophysiological studies and rapid evaluation of new therapies. Fresh whole core bone marrow (BM) biopsies taken from 33 myeloma patients were engrafted into the hind limb muscle of severe combined immunodeficient (SCID) mice. Human Ig was detected in 28/33 mice and three grew palpable tumors displaying many features of human myeloma including morphology, immunophenotype and BM plasmacytosis. Following intramuscular passage, we generated large numbers of mice with predictable increases in tumor growth and human paraprotein levels. We further characterized the model generated from an IgGÏ-producing tumor known as LAGÏ-1 and determined the effects of the proteasome inhibitor bortezomib, the alkylating agent melphalan, and the DNA damaging agent liposomal doxorubicin, on the growth of this tumor. LAGÏ-1-bearing mice receiving higher doses of bortezomib showed reduced tumor growth whereas a lower dose had no effect. In contrast, melphalan did not significantly alter tumor growth, except minimally at high doses, reflecting the resistance of this patient's tumor to this drug. We also used our intramuscular (i.m.) LAGÏ-1 model to optimize the dosing schedule of liposomal doxorubicin. Low doses administered once daily three days per week decreased tumor growth and human paraprotein levels whereas much higher doses given once weekly had no anti-myeloma effects. Furthermore, LAGÏ-1 cells produce local tumors when injected subcutaneously and lytic lesions when injected intravenously allowing for multiple methods of evaluating the anti-myeloma effects of a variety of agents. Our new clinically relevant SCID models of human myeloma should greatly facilitate drug development and enable novel therapies to quickly move from the laboratory to the clinic.
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. Disclosures Berenson: Takeda: Consultancy, Honoraria, Speakers Bureau; Celgene: Consultancy, Honoraria, Speakers Bureau; Bristol-Myers Squibb: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Incyte: Honoraria, Patents & Royalties: OncoTracker, Speakers Bureau; Amgen: Consultancy, Honoraria, Speakers Bureau. Swift:Jassen: Consultancy, Honoraria, Speakers Bureau; bristol myers squibb: Consultancy, Honoraria, Speakers Bureau; Amgent: Consultancy, Honoraria, Speakers Bureau. Boccia:Incyte: Consultancy, Honoraria, Research Funding, Speakers Bureau; Daiichi Sankyo: Consultancy, Honoraria, Research Funding, Speakers Bureau; Amgen: Consultancy, Honoraria, Research Funding, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Research Funding, Speakers Bureau; Genentech: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Rigel: Consultancy, Honoraria, Research Funding, Speakers Bureau. OffLabel Disclosure: Ruxolitinib and steroids only for treatment patients with 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. Disclosures Vescio: Janssen: Speakers Bureau; Karyopharm: Speakers Bureau; GlaxoSnithKlein: Speakers Bureau; Amgen: Speakers Bureau. OffLabel Disclosure: Ruxolitinib is being investigated off-label to determine if it shows anti-myeloma activity in combination with steroids for relapsed/refractory myeloma patients.
4936 Despite recent advances in the treatment of MM, the disease remains incurable and many of the most effective, newer combination therapies are accompanied by significant side effects that have a major negative impact on the patient's quality of life. Pegylated liposomal doxorubicin (PLD) and bortezomib have shown anti-MM efficacy in the laboratory and for the treatment of previously treated MM patients, leading to FDA approval for patients who have failed one prior therapy. Using our severe combined immunodeficiency-hu murine models of human MM, we have previously demonstrated that lower doses of PLD administered daily are more effective and better tolerated than higher amounts given weekly. Moreover, the combination of bortezomib and dexamethasone has been shown to be effective for previously untreated MM patients. Prior studies by our group have shown that combining chemotherapy including PLD with bortezomib administered at 1.0 mg/m2 on days 1, 4, 8, and 11 of a 28-day cycle rather than the standard 1.3 mg/m2 on the same days of a 21-day schedule is effective for MM patients with relapsed or refractory disease and associated with a reduction in the incidence and severity of peripheral neuropathy. Thus, we conducted a single-arm multi-center phase II study for previously untreated MM patients to evaluate the combination of intravenously administered dexamethasone, bortezomib and PLD (DVD). The treatment consisted of intravenous administration of 40 mg dexamethasone followed by 1.0 mg/m2 bortezomib and finally 5.0 mg/m2 PLD on days 1, 4, 8, and 11 of a 28-day cycle. Patients were treated to a maximum response plus two additional cycles or completed a maximum of eight cycles of therapy without disease progression. To date, 22 (of 35 planned) patients have been enrolled with a median age of 64 years (range, 42-79 years). The majority of those on study (68 %) were diagnosed with International Staging System II or III MM. Four patients are too early to assess for response. To date, among the 18 evaluable patients, 16 (89%) have shown objective responses to the DVD regimen, including 2 complete responses (11%), 8 partial responses (44%) and 6 minimal responses (33%). The other 2 patients (11%) had stable disease, with one of these subjects showing a continuing reduction in M-protein after 2 cycles of therapy to date. Thus, disease control was achieved in all patients. To date, no patient has shown progressive disease after 2+ - 12+ months of follow-up. Six patients experienced grade 3 adverse events and one patient with a prior history of pulmonary interstitial fibrosis developed a grade 4 toxicity (shortness of breath). Grade 3 adverse events in three of the six patients were judged not to be related to the study treatment. The most common grade 3 adverse event was reversible neutropenia (n=2). To date, only 2 patients (9%) have developed peripheral neuropathy (grade 1). Notably, there have been no cases of stomatitis or hand-foot syndrome. Thus, these results suggest that the DVD regimen using a modified schedule and doses of the combination of intravenous dexamethasone, bortezomib and PLD is a well tolerated treatment that produces high response rates for previously untreated patients with multiple myeloma. Disclosures Berenson: Millennium Pharmaceuticals: Consultancy, Research Funding, Speakers Bureau; Centocor Ortho Biotech: Consultancy, Speakers Bureau. Hilger:Millennium Pharmaceutcals: Employment.
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