MEI Pharma Announces Pre-Specified Response Rate Exceeded in Dose-Escalation Study of ME-401 in Chronic Lymphocytic Leukemia and Follicular Lymphoma

SAN DIEGO, May 31, 2017 /PRNewswire/ --

-Independent Safety Review Committee Finds No Dose Limiting Toxicities, Declares Minimum Biologically Effective Dose, Recommends Dose Escalation

-Full Data to be Submitted for Presentation at Upcoming Scientific Meeting

MEI Pharma, Inc. (Nasdaq: MEIP), an oncology company focused on the clinical development of novel therapies for cancer, today announced that an independent Safety Review Committee completed its pre-specified review of the first cohort of six evaluable patients in a Phase Ib, open-label, dose-escalation study of the Company's investigational drug candidate ME-401, a potent and selective oral PI3K delta inhibitor, in relapsed/refractory chronic lymphocytic leukemia (CLL) and follicular lymphoma.

Based on its review of the safety and efficacy data, the Safety Review Committee declared a minimum biologically effective dose (mBED) for ME-401 at the starting dose of 60 mg and recommended escalation to a 120 mg dose cohort. According to the study protocol, the mBED is defined as a dose that is safe and achieves a response in at least three of six patients. Response assessments are based on criteria of the International Workshop on Chronic Lymphocytic Leukemia for patients with CLL or the Lugano Classification for patients with follicular lymphoma. Response is initially assessed after 8 weeks of therapy.

To date, all six patients have been on study for a minimum of 10 weeks (range, 10-28 weeks). There have been no reports of ALT/AST elevations, colitis or pneumonitis, events commonly reported with other drugs in this class. One patient in the study experienced grade 3 neutropenia that was considered related to study drug. All other adverse events reported were grades 1 or 2. No patients have discontinued due to adverse events. Full data will be submitted for presentation at an upcoming scientific meeting.

"Given the high bar we have placed on the ME-401 program, we are very pleased with the early safety and efficacy data from this study," said Daniel P. Gold, Ph.D., President and Chief Executive Officer of MEI Pharma. "PI3K delta inhibitors have demonstrated clear activity in the treatment of CLL and follicular lymphoma, but at the expense of well-defined and substantial toxicities. We believe this provides an opportunity for a highly differentiated drug that is both effective and safe. Now we look forward to demonstrating the therapeutic index of ME-401 across multiple dose cohorts and presenting detailed results later this year."

ME-401 is a highly differentiated oral PI3K delta inhibitor that has a distinct chemical structure from other drugs in its class, including the approved drug idelalisib (marketed as Zydelig^®). Results from a Phase I first-in-human study of ME-401 showed levels of drug exposure that support the potential for an improved therapeutic window compared to idelalisib, with a half-life that supports once-daily dosing.

The ongoing Phase Ib study is designed to determine the minimum biologically effective dose, maximally tolerated dose, dose limiting toxicities and recommended Phase 2 dose of ME-401 while evaluating its safety, efficacy and pharmacokinetics. The study, which opened for enrollment in September 2016, is expected to enroll up to 84 patients at approximately 10 sites. Additional information regarding the study, including inclusion and exclusion criteria, is available at www.clinicaltrials.gov (identifier: NCT02914938).

About ME-401

ME-401 (formerly PWT143) is an orally bioavailable, potent and selective inhibitor of phosphatidylinositol 3 kinase (PI3K) delta, a molecular target that has been shown to play a critical role in the proliferation and survival of certain hematologic cancer cells. Results from a first-in-human, single ascending dose clinical study of ME-401 in healthy volunteers were presented at the American Association for Cancer Research Annual Meeting in April 2016. The data demonstrated on-target activity at very low plasma concentrations and suggest that ME-401 has a superior pharmacokinetic and pharmacodynamic profile compared to idelalisib. The U.S. Food and Drug Administration approved an Investigational New Drug application for ME-401 in B-cell malignancies in March 2016.

MEI Pharma owns exclusive worldwide rights to ME-401.

About MEI Pharma

MEI Pharma, Inc. (Nasdaq: MEIP) is a San Diego-based oncology company focused on the clinical development of novel therapies for cancer. The Company's portfolio of drug candidates includes Pracinostat, an oral HDAC inhibitor that is partnered with Helsinn Healthcare, SA. Pracinostat has been granted Breakthrough Therapy Designation from the U.S. Food and Drug Administration for use in combination with azacitidine for the treatment of patients with newly diagnosed AML who are unfit for intensive chemotherapy. Pracinostat is also being developed in combination with azacitidine for the treatment of patients with high and very high-risk myelodysplastic syndrome. MEI Pharma's clinical development pipeline also includes ME-401, a highly differentiated oral PI3K delta inhibitor currently in a Phase Ib study in patients with relapsed/refractory CLL or follicular lymphoma. The Company is also developing ME-344, a novel mitochondrial inhibitor currently in an investigator-sponsored study in combination with bevacizumab for the treatment of HER2-negative breast cancer. Pracinostat, ME-401 and ME-344 are investigational agents and are not approved for use in the U.S. For more information, please visit www.meipharma.com.

Under U.S. law, a new drug cannot be marketed until it has been investigated in clinical studies and approved by the FDA as being safe and effective for the intended use. Statements included in this press release that are not historical in nature are "forward-looking statements" within the meaning of the "safe harbor" provisions of the Private Securities Litigation Reform Act of 1995. You should be aware that our actual results could differ materially from those contained in the forward-looking statements, which are based on management's current expectations and are subject to a number of risks and uncertainties, including, but not limited to, our failure to successfully commercialize our product candidates; costs and delays in the development and/or FDA approval, or the failure to obtain such approval, of our product candidates; uncertainties or differences in interpretation in clinical study results; our inability to maintain or enter into, and the risks resulting from our dependence upon, collaboration or contractual arrangements necessary for the development, manufacture, commercialization, marketing, sales and distribution of any products; competitive factors; our inability to protect our patents or proprietary rights and obtain necessary rights to third party patents and intellectual property to operate our business; our inability to operate our business without infringing the patents and proprietary rights of others; general economic conditions; the failure of any products to gain market acceptance; our inability to obtain any additional required financing; technological changes; government regulation; changes in industry practice; and one-time events. We do not intend to update any of these factors or to publicly announce the results of any revisions to these forward-looking statements.

SOURCE MEI Pharma, Inc.

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