ALBERT

Beschreibung: Introduction: Belumosudil (KD025) is a novel oral selective rho-associated coiled-coil kinase 2 (ROCK2) inhibitor specifically designed for the treatment of cGVHD, an immune-mediated inflammatory and fibrotic disorder. In a previous dose-finding study (KD025-208, N=54), two-thirds of patients, including those with fibrotic and inflammatory manifestations, achieved a partial or complete response with belumosudil. Herein, we report on the top-line results (6 months after the last patient in) from the pivotal phase 2 trial (ROCKstar [KD025-213], N=132). Methods: This phase 2, open-label, randomized, multicenter study evaluated belumosudil 200 mg QD (n=66) and BID (n=66) in patients with cGVHD who received 2 to 5 prior lines of therapy (LOT). Treatment continued until clinically significant progression of cGVHD. The primary end point was overall response rate (ORR), defined per the 2014 National Institutes of Health Consensus Criteria. Additional end points included duration of response (DOR), Lee Symptom Scale (LSS) score, failure-free survival (FFS), corticosteroid (CS) dose reductions and overall survival. The study was powered such that the lower bound of the 95% confidence interval (CI) excludes 30%, with appropriate multiplicity adjustment. Results: At enrollment, the median age was 56 years, the median time from cGVHD diagnosis to enrollment was 29 months, 67% of patients had severe cGVHD, 52% had ≥4 organs involved, 72% had received ≥3 prior LOT (including ibrutinib [n=46] or ruxolitinib [n=38]) and 73% were refractory to their last LOT. The baseline characteristics of both arms were well balanced. With a median follow-up of 8 months, the ORR (95% CI) with belumosudil 200 mg QD and BID was 73% (60%-83%) and 74% (62%-84%), respectively (Table 1). In patients who previously received ruxolitinib (29%), the ORR with belumosudil 200 mg QD and BID was 65% (41%-85%) and 72% (47%-90%), respectively. In patients who previously received ibrutinib (35%), the ORR with belumosudil 200 mg QD and BID was 73% (50%-89%) and 71% (49%-87%), respectively. High ORRs were seen in all patient subgroups, regardless of length of time from diagnosis to treatment, including those with severe cGVHD, involvement of ≥4 organs and a refractory response to prior LOT (Figure 1). The response rate was similar across all affected organs. The median time to response was 4 weeks. Of responders, 49% have maintained response for ≥20 weeks. The median DOR has not yet been reached. Clinically meaningful improvement (≥7-point reduction) in LSS score on consecutive assessments was observed in 39% and 33% of patients in the QD and BID groups, respectively. Both responders (43%) and nonresponders (17%) experienced a clinically meaningful improvement in LSS score. FFS was 77% (69%-84%) at 6 months. CS and calcineurin inhibitor discontinuations were seen in 18% and 13% of patients, respectively. Belumosudil was well tolerated, with 〉95% relative dose intensity in 83% of patients. Drug discontinuation occurred in 10% of patients due to possible drug-related adverse events (AEs), 3% due to progression of underlying disease and 12% due to progression of cGVHD. AEs were consistent with those expected in patients with cGVHD receiving CS and other immunosuppressants (Table 2). Common AEs included fatigue (32%), diarrhea (29%), nausea (26%), cough (24%), dyspnea (24%), upper respiratory tract infection (23%), peripheral edema (21%) and headache (20%). At least 1 serious AE occurred in 34% of patients. Twenty-three percent of patients had at least 1 liver-related investigation; the most common was increased gamma-glutamyltransferase (11%), and only 1 patient showed an increase in bilirubin. Eight patients died during the study; 5 due to AEs (1 possibly related to belumosudil) and 3 during long-term follow-up (〉28 days after last dose). There were no reports of cytomegalovirus reactivation or infection. Conclusion: Treatment with belumosudil at both doses resulted in high ORRs across key subgroups, meeting the primary end point of this pivotal randomized trial in cGVHD. Responses were durable and clinically meaningful, irrespective of patient and cGVHD characteristics, and were seen in patients who previously received ruxolitinib and ibrutinib. Belumosudil was well tolerated, with limited and manageable AEs. Further studies will evaluate its use earlier in disease management. The 12-month data analysis will be presented at ASH 2020. Disclosures Cutler: Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees; Kadmon: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees; Medsenic: Consultancy, Membership on an entity's Board of Directors or advisory committees; Generon: Consultancy, Membership on an entity's Board of Directors or advisory committees; Mesoblast: Consultancy, Membership on an entity's Board of Directors or advisory committees. Lee:Pfizer: Consultancy, Research Funding; Incyte: Consultancy, Research Funding; Amgen: Research Funding; Kadmon: Research Funding; AstraZeneca: Research Funding; Novartis: Research Funding; Takeda: Research Funding; Syndax: Research Funding. Rotta:Merck: Speakers Bureau; Jazz Pharma: Speakers Bureau. Ramakrishnan:Amgen: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Cigna: Honoraria. Eiznhamer:Kadmon Corporation, LLC: Current Employment, Current equity holder in publicly-traded company. Schueller:Kadmon Corporation, LLC: Current Employment, Current equity holder in publicly-traded company. Yang:Kadmon Corporation, LLC: Current Employment, Current equity holder in publicly-traded company. Green:Kadmon Corporation, LLC: Current Employment, Current equity holder in publicly-traded company. Aggarwal:Kadmon Corporation, LLC: Consultancy; Angiocrine Bioscience, Inc: Current Employment, Other: stock options. Blazar:BlueRock Therapeutics: Research Funding; BlueRock Therapeuetic: Consultancy; Fate Therapeutics Inc.: Research Funding; Magenta Therapeutics: Consultancy; Childrens' Cancer Research Fund: Research Funding; KidsFirst Fund: Research Funding; Tmunity: Other: Co-founder. Jagasia:Ocugen: Other; Mallinckrodt: Research Funding; Janssen: Research Funding.

Beschreibung: Myeloproliferative neoplasms (MPNs) are a group of hematopoietic stem cell disorders driven by mutations that constitutively activate physiologic signal transduction pathways essential for hematopoiesis. The majority of patients with classical MPNs harbor mutations within the Janus activated kinase 2 (JAK2), calreticulin (CALR), or thrombopoietin receptor (MPL) genes. The occurrence of driver mutations among patients is mutually exclusive but rare double positive cases have been reported. Employment of targeted sequencing methods for diagnostics revealed more double positive cases and reviewing published studies we estimate the CALR and JAK2 double positive MPN frequency to be about 0.5% in all MPNs and 2% in essential thrombocythemia. However, the mutual exclusivity of CALR and JAK2 mutations in double positive cases was confirmed at single cell level in few studies where clonogenic assays were performed with subsequent genotyping of colonies. In our MPN biobank of over 800 samples, we identified one case diagnosed with PMF, carrying both in JAK2 and CALR, with allelic burdens of 8% and 41%, respectively. Using a clonogenic assay, we confirmed mutual exclusivity of the mutations at CFU level confirming previous findings. Mutations can be mutually exclusive due to their synthetic lethal interaction. Such synthetic lethal interaction has been recently described in splicing factor mutated MDS, showing that SF3B1 and SRSF2 double mutant hematopoietic cells (HSC) have reduced fitness in vivo providing explanation why such patients are never observed. In this study, we tested the hypothesis that JAK2-V617F and CALR-del52 mutations are synthetic lethal if they occur in the same HSC. We have generated mice that co-expresses both JAK2-V617F and CALR-del52 mutations in hematopoietic lineages and analyzed their phenotype. First, we co-expressed JAK2-V617F and CALR-del52 on the Vav1-Cre backgound in which Cre recombinase activates the floxed transgenes in embryonic HSC. Double positive offspring were born at expected Mendelian frequency compared to single positive littermates, suggesting no signs of synthetic lethality in utero. The phenotype of the JAK2-V617F and CALR-del52 double positive mice was significantly more severe compared to single mutant mice. More specifically, double positive mice showed more pronounced splenomegaly, higher white blood cell, lymphocyte, granulocyte, monocyte, and platelet counts in peripheral blood. In the bone marrow, double positive mice had more prominent megakaryocyte dyspoiesis and altered myeloid to erythroid ratios, without evident myelofibrosis as observed in histological sections. This increase in megakaryocyte numbers was also confirmed by FACS. In addition, double positive mice had more obscured follicular architecture and more signs of enhanced extramedullary hematopoiesis in the spleen, and more pronounced megakaryocytic sequestration in the lungs when compared to the JAK2-V617F histology findings. These mice also had lower overall survival compared to the JAK2-V617F and CALR-del52 mice. Next, we performed competitive bone marrow transplantation (BMT) to examine HSC fitness in primary and secondary transplants. Wild type bone marrow (BM) derived from F1 hybrid CD45.1/CD45.2 mice was mixed with BM form either mice bearing single mutation or double mutations (CD45.2), and ingrafted into CD45.1 recipients. The changes in chimerism were followed in peripheral blood by FACS. Double positive BM engrafted recipients equally well as JAK2-V617F or CALR-del52 cells suggesting no functional defect at HSC level. Same results were seen also in secondary BMT. In summary, double positive mice have an enhanced MPN phenotype with lower overall survival compared to single positive JAK2-V617F and CALR-del52 animals. Our results suggest that the mutual exclusivity of MPN driver mutations JAK2-V617F and CALR-del52 is not due to synthetic lethality or loss of HSC fitness. It is possible that once the second mutation is acquired, JAK2-V617F and CALR-del52 double positive cells do not gain additional competitive advantage over single positive HSCs, and therefore, do not grow out into a significant population. Another reason why we do not observe JAK2-V617F and CALR-del52 double positive colonies in patients is the very low likelihood of such HSC arising. Our data shows that such MPN patients may be found and very likely will have more severe MPN. Disclosures No relevant conflicts of interest to declare.