Purpose: Myelofibrosis is characterized by bone marrow fibrosis, atypical megakaryocytes, splenomegaly, constitutional symptoms, thrombotic and hemorrhagic complications, and a risk of evolution to acute leukemia. The JAK kinase inhibitor ruxolitinib provides therapeutic benefit, but the effects are limited. The purpose of this study was to determine whether targeting AURKA, which has been shown to increase maturation of atypical megakaryocytes, has potential benefit for patients with myelofibrosis. Patients and Methods: Twenty-four patients with myelofibrosis were enrolled in a phase I study at three centers. The objective of the study was to evaluate the safety and preliminary efficacy of alisertib. Correlative studies involved assessment of the effect of alisertib on the megakaryocyte lineage, allele burden, and fibrosis. Results: In addition to being well tolerated, alisertib reduced splenomegaly and symptom burden in 29% and 32% of patients, respectively, despite not consistently reducing the degree of inflammatory cytokines. Moreover, alisertib normalized megakaryocytes and reduced fibrosis in 5 of 7 patients for whom sequential marrows were available. Alisertib also decreased the mutant allele burden in a subset of patients. Conclusions: Given the limitations of ruxolitinib, novel therapies are needed for myelofibrosis. In this study, alisertib provided clinical benefit and exhibited the expected on-target effect on the megakaryocyte lineage, resulting in normalization of these cells and reduced fibrosis in the majority of patients for which sequential marrows were available. Thus, AURKA inhibition should be further developed as a therapeutic option in myelofibrosis. See related commentary by Piszczatowski and Steidl, p. 4868
Background Protein arginine methyltransferase 5 (PRMT5) is the primary enzyme responsible for symmetric arginine dimethylation of multiple proteins that impact cell proliferation. Its substrates include proteins involved in mRNA splicing, signal transduction, gene transcription, and DNA repair. PRMT5 overexpression occurs in many cancers and correlates with poor prognosis. GSK3326595 is a potent, specific, and reversible inhibitor of PRMT5 that inhibits proliferation and induces cell death in a broad range of solid and hematologic tumor cell lines. It also exhibits potent anti-tumor activity in vivo in animal models, including in preclinical models of myeloid malignancies. One mechanism of action of GSK3326595 is via inhibition of cellular mRNA splicing and upregulation of tumor suppressor function. Mutations in splicing factors are frequent in myeloid malignancies (including approximately 40% of patients with myelodysplastic syndrome [MDS], and over 60% of patients with chronic myelomonocytic leukemia [CMML]), and further inhibition of mRNA splicing via GSK3326595 may lead to a synthetic lethal phenotype specifically in splicing mutant disease. Study 208809 is the first trial of a PRMT5 inhibitor in participants with myeloid malignancies. Methods Study 208809 is a Phase I/II study to evaluate the safety, tolerability, and clinical activity of GSK3326595 monotherapy in participants with relapsed and refractory MDS, CMML, and hypoproliferative acute myeloid leukemia (AML) that has evolved from an antecedent MDS. Part 1 will identify a tolerated dose and establish preliminary evidence of efficacy in this population. At the end of Part 1, if pre-specified criteria are met, then the study will be expanded with three additional Parts that will be opened in parallel. Part 2A is a Phase II randomized comparison of monotherapy GSK3326595 versus investigator's choice of best available care in participants with relapsed and refractory MDS, CMML, and hypoproliferative AML. Part 2B is a single-arm investigation of safety and efficacy of GSK3326595 plus 5-azacitidine in participants with newly diagnosed high-risk MDS. Part 2C is a single-arm investigation of the safety and efficacy of monotherapy GSK3326595 in participants with relapsed or refractory AML whose tumors harbor mutations in components of the pre-mRNA splicing machinery. All participants enrolled in this study have a diagnosis of MDS, CMML, or AML, with enrollment into each cohort as defined above. Participants are adults with adequate organ function as defined in the protocol. Prior allogeneic transplant is permitted. There are no required biomarkers for enrollment to Parts 1, 2A, and 2B, though central confirmation of pre-mRNA splicing factor mutations will be performed to stratify participants for overall analysis. Enrollment to Part 2C is limited to participants with splicing factor mutations. It is estimated that a maximum of 302 participants will be enrolled in the study, divided as follows: Approximately 41 participants in Part 1, approximately 192 participants in Part 2A, approximately 41 participants in Part 2B, and approximately 28 participants in Part 2C. In Part 1, the primary endpoint is clinical benefit rate, as defined as the percentage of participants achieving a complete remission, complete marrow remission, partial remission (PR), stable disease lasting at least 8 weeks, or hematologic improvement, as per standard criteria. In Part 2A, the primary endpoint is overall survival. In Part 2B and Part 2C, the primary endpoint is overall response rate (ORR), defined as the percentage of participants achieving a PR or better. Samples are collected to evaluate symmetric dimethylated arginine (SDMA), the enzymatic product of PRMT5. This has been demonstrated to be a pharmacodynamic marker of PRMT5 inhibition in plasma and tumor tissue. In addition, participants will be stratified based on the presence or absence of spliceosome mutations and analyzed separately to evaluate the effect of these mutations on clinical activity. As of 1 August 2019, recruitment is ongoing across six centers in the United States and Canada; ten participants have been enrolled, all into Part 1. ClinicalTrials.gov identifier: NCT03614728 Study is funded by GlaxoSmithKline Disclosures Watts: Takeda: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Bradley:AbbVie: Other: Advisory Board. Brunner:Novartis: Research Funding; Jazz Pharma: Membership on an entity's Board of Directors or advisory committees; Forty Seven Inc: Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding. Minden:Trillium Therapetuics: Other: licensing agreement. Papadantonakis:Agios: Consultancy, Honoraria. Abedin:Actinium Pharmaceuticals: Research Funding; Pfizer Inc: Research Funding; Helsinn Healthcare: Research Funding; Agios: Honoraria; Jazz Pharmaceuticals: Honoraria. Baines:GlaxoSmithKline: Employment, Equity Ownership. Barbash:GlaxoSmithKline: Employment, Equity Ownership, Patents & Royalties, Research Funding. Gorman:GlaxoSmithKline: Employment, Equity Ownership. Kremer:GlaxoSmithKline: Employment, Equity Ownership. Borthakur:Cantargia AB: Research Funding; Eisai: Research Funding; Tetralogic Pharmaceuticals: Research Funding; Argenx: Membership on an entity's Board of Directors or advisory committees; FTC Therapeutics: Membership on an entity's Board of Directors or advisory committees; BioTheryX: Membership on an entity's Board of Directors or advisory committees; Xbiotech USA: Research Funding; Novartis: Research Funding; Oncoceutics: Research Funding; Oncoceutics, Inc.: Research Funding; PTC Therapeutics: Consultancy; BioLine Rx: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Agensys: Research Funding; AstraZeneca: Research Funding; Bayer Healthcare AG: Research Funding; BMS: Research Funding; Eli Lilly and Co.: Research Funding; NKarta: Consultancy; Cyclacel: Research Funding; GSK: Research Funding; Janssen: Research Funding; Incyte: Research Funding; AbbVie: Research Funding; Merck: Research Funding; Arvinas: Research Funding; Polaris: Research Funding; Strategia Therapeutics: Research Funding.
In preclinical studies, the LSD1 inhibitor tranylcypromine (TCP) combined with alltrans retinoic acid (ATRA) induces differentiation and impairs survival of myeloid blasts in non-APL acute myeloid leukemia (AML). We conducted a Phase I clinical trial (NCT02273102) to evaluate the safety and activity of ATRA plus TCP in patients with relapsed/refractory AML and myelodysplasia (MDS).Experimental Design: Seventeen patients were treated with ATRA and TCP (3 dose levels: 10 mg twice daily [BID], 20 mg BID, and 30 mg BID).Results: ATRA-TCP had an acceptable safety profile. The maximum tolerated dose of TCP was 20 mg BID. Best responses included 1 morphologic leukemia-free state, 1 marrow complete remission with hematologic improvement, 2 stable disease with hematologic improvement, and 2 stable disease. By intention-to-treat, the overall response rate was 23.5% and clinical benefit rate
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