(MEIP) High Response Rates Phase II Study Of Pracinostat In Acute Myeloid Leukemia

Study Meets Pre-Specified CR/CRi Rate in First Nine Patients

SAN DIEGO, June 10, 2014  — MEI Pharma, Inc. (Nasdaq: MEIP), an oncology company focused on the clinical development of novel therapies for cancer, today announced preliminary response data from the first stage of a two-stage, open-label Phase II clinical study of its investigational drug candidate Pracinostat in combination with Vidaza^® (azacitidine) in elderly patients with newly diagnosed acute myeloid leukemia (AML) who are unsuitable for intensive chemotherapy.

Of the first nine patients enrolled in the multicenter study, two achieved a complete response (CR) and one achieved a complete response with incomplete blood count recovery (CRi), each following one or two treatment cycles. These data met the pre-specified CR/CRi rate required to advance to the second stage of the study. In addition, three patients achieved a partial response (PR) or a partial response with incomplete blood count recovery (PRi) after their initial or second treatment evaluation, for an overall response rate of 67%.

“We are very encouraged by these early data,” said Robert D. Mass, MD, Chief Medical Officer of MEI Pharma. “The protocol-specified CR/CRi rate with Vidaza alone in this patient population is 10%, so this early observed rate of 33% is particularly noteworthy. The similarity of the high response rate seen to date in this study with those observed in our pilot study in higher risk myelodysplastic syndrome (MDS) further increases our confidence in the combination of Pracinostat and Vidaza. This combination is also being assessed in our ongoing, placebo-controlled Phase II study in front line MDS. We look forward to sharing additional data from our front line AML study at a scientific conference later this year.”

The open-label Phase II study of Pracinostat and Vidaza in front line AML is a two-stage design, with progression to the second stage dependent upon achieving a pre-specified milestone. According to the study protocol, if three or more patients achieved a CR or a CRi within the first 27 patients, the trial will continue to enroll an additional 13 patients in the second stage, for a total of 40 evaluable patients. To date, 12 patients have been enrolled in the study, three of which are still too early for a clinical response assessment.

The combination of Pracinostat and Vidaza has been generally well tolerated in the study, with no new or more severe adverse events than previously reported, including fatigue, myelosuppresion and gastrointestinal toxicity (nausea, vomiting, diarrhea).

The Phase II study is being conducted in collaboration with Dr. Guillermo Garcia-Manero and the MD Anderson Cancer Center. The primary endpoint of the trial is CR/CRi rate. Secondary endpoints include overall response rate, complete cytogenetic/molecular response, duration of response, progression-free survival and overall survival. Additional information regarding the trial, including eligibility and locations, is available at www.clinicaltrials.gov.

About Pracinostat

Pracinostat is an oral histone deacetylase (HDAC) inhibitor that has been tested in a number of Phase I and Phase II clinical trials in advanced hematologic disorders and solid tumor indications in both adult and pediatric patients. Pracinostat has been generally well tolerated in more than 250 patients to date, with readily manageable side effects that are often associated with drugs of this class, including fatigue, myelosuppresion and gastrointestinal toxicity. In a Phase I dose-escalation trial, Pracinostat demonstrated evidence of single-agent activity in elderly AML patients, including two out of 14 (14%) who achieved a CR, with durable responses persisting 206+ and 362 days, respectively. In addition, results from a pilot study of Pracinostat in combination with Vidaza in patients with advanced MDS showed an overall response rate of 90% (nine out of 10), including eight patients who achieved either a CR or a CRi.

MEI Pharma owns exclusive worldwide rights to Pracinostat.

About AML

Acute myeloid leukemia (also known as acute myelogenous leukemia) is the most common acute leukemia affecting adults, and its incidence is expected to increase as the population ages. The American Cancer Society estimates about 14,590 new cases of AML per year in the U.S., with an average age of about 66. Treatment options for AML remain virtually unchanged over the past 30 years. Front line treatment consists primarily of chemotherapy, while the National Comprehensive Cancer Network (NCCN) Clinical Practice Guidelines in Oncology recommend Vidaza or Dacogen^® (decitabine) as low intensity treatment options for AML patients over the age of 60 who are unsuitable for induction chemotherapy.

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 lead drug candidate is Pracinostat, a potential best-in-class, oral HDAC inhibitor currently being developed for MDS and AML. MEI Pharma is also developing ME-344, a mitochondrial inhibitor that has shown evidence of single-agent activity in a first-in-human clinical study in patients with refractory solid tumors, including eight of 21 evaluable patients (38%) who achieved stable disease or better. In September 2013, the Company further expanded its pipeline of drug candidates with the acquisition of PWT143, a highly selective PI3-kinase delta inhibitor. For more information, go to www.meipharma.com.

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