CTI Biopharma Corp. (CTI BioPharma) (NASDAQ: CTIC) today announced that results from the Phase 3 PERSIST-2 clinical trial of pacritinib (an investigational JAK2 inhibitor) have been published online in JAMA Oncology. The randomized, international, multicenter study compared the efficacy and safety of pacritinib at two dose levels, compared with best available therapy (BAT), which included ruxolitinib (a JAK1/JAK2 inhibitor), in patients with myelofibrosis and thrombocytopenia (defined as platelet counts ≤100 x 10⁹/L). 

In the intent-to-treat patient population of the study, the combined pacritinib arms (400mg once daily and 200mg twice daily dosing, 149 patients total) demonstrated a significant improvement of 35% or more in spleen volume reduction (SVR) at 24 weeks of treatment in 27 patients (18%) compared to 2 patients (3%) out of 72 patients in the BAT arm, which included treatment with ruxolitinib (P=0.001). The combined pacritinib treatment arms also demonstrated a greater than 50% reduction in total symptom score (TSS) in 37 patients (25%), compared to 10 patients (14%) in the BAT arm (P=0.079). Additionally, an exploratory analysis of the 74 patients who received pacritinib 200mg twice daily showed an improvement of 35% or more reduction of SVR in 16 patients (22%; P=0.001 vs BAT) and 50% or greater reduction of TSS in 24 patients (32%; P=0.01 vs BAT).

Pacritinib was generally well tolerated. The most commonly reported (≥15%) nonhematologic adverse events with pacritinib were gastrointestinal events, fatigue, peripheral edema, and dizziness, and those with BAT (including 19 patients with watchful-waiting only) were abdominal pain, fatigue, diarrhea, and peripheral edema. The majority of common nonhematologic adverse events were grade 1 or 2 in severity. Diarrhea was the most frequently observed adverse event with pacritinib (53% grade 1/2; 4% grade 3) most often occurring during weeks 1 to 8. The incidence of diarrhea was lower with pacritinib twice daily dosing compared to once daily dosing (48% vs 67%, respectively). Diarrhea was manageable with standard antidiarrheal agents (e.g., loperamide) and generally resolved within 1 to 2 weeks. The rate of on-study death was lowest with pacritinib twice daily (6%) compared to BAT (9%) and pacritinib once daily (14%).

Cardiac events were reported at similar rates in all arms (32%, pacritinib once daily or twice daily; 28%, BAT) and were most commonly peripheral edema in all arms. Grade 3 or 4 cardiac events were reported in 13 patients (13%) treated with pacritinib once daily, 7 patients (7%) treated with pacritinib twice daily, and 9 patients (9%) treated with BAT.

Bleeding events were reported at similar rates in all arms (36%, 42%, and 41% of patients treated with pacritinib once daily, twice daily, and BAT, respectively) and were most commonly epistaxis in all arms. Grade 3 or 4 bleeding events were reported in 7 patients (7%), 15 patients (14%), and 7 patients (7%) treated with pacritinib once daily, twice daily, and BAT, respectively.

"Pacritinib was shown to reduce both spleen volume and total symptom score, two very important clinical measures, in myelofibrosis patients with thrombocytopenia including those patients who received prior treatment with ruxolitinib," stated John Mascarenhas, M.D., Adult Leukemia Program, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai. "Clinical improvements in hemoglobin levels and reduction in transfusions were also seen in patients who received pacritinib, and pacritinib had a generally manageable safety profile."

Dr. Mascarenhas continued, "Myelofibrosis is a difficult and progressive disease, and patients with thrombocytopenia that have already received JAK2 inhibitor therapy have an especially poor prognosis. These study results indicate there is important potential clinical benefit of pacritinib for these patients."

The PERSIST-2 trial results were previously presented at the 58th American Society of Hematology (ASH) Annual Meeting, in December 2016.

CTI BioPharma is currently enrolling patients in the PAC203 study, which is evaluating the safety and efficacy of three dosing schedules, including 200mg twice daily (BID), 100mg twice daily (BID), and 100mg once daily (QD).

About CTI BioPharma Corp.

CTI BioPharma Corp. is a biopharmaceutical company focused on the acquisition, development and commercialization of novel targeted therapies covering a spectrum of blood-related cancers that offer a unique benefit to patients and healthcare providers. CTI BioPharma has a late-stage development pipeline, including pacritinib for the treatment of patients with myelofibrosis. CTI BioPharma is headquartered in Seattle, Washington.

About Pacritinib

Pacritinib is an investigational oral kinase inhibitor with specificity for JAK2, FLT3, IRAK1 and CSF1R. The JAK family of enzymes is a central component in signal transduction pathways, which are critical to normal blood cell growth and development, as well as inflammatory cytokine expression and immune responses. Mutations in these kinases have been shown to be directly related to the development of a variety of blood-related cancers, including myeloproliferative neoplasms, leukemia and lymphoma. In addition to myelofibrosis, the kinase profile of pacritinib suggests its potential therapeutic utility in conditions such as acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), chronic myelomonocytic leukemia (CMML), and chronic lymphocytic leukemia (CLL), due to its inhibition of c-fms, IRAK1, JAK2 and FLT3.

About Myelofibrosis and Myeloproliferative Neoplasms

Myelofibrosis is one of three main types of myeloproliferative neoplasms (MPN), which are a closely related group of progressive blood cancers. The three main types of MPNs are primary myelofibrosis (PMF), polycethemia vera (PV) and essential thrombocythemia (ET).

Myelofibrosis is a serious and life-threatening bone marrow disorder caused by the accumulation of malignant bone marrow cells that triggers an inflammatory response and scars the bone marrow. The replacement of bone marrow with scar tissue limits its ability to produce red blood cells, prompting the spleen and liver to take over this function. Symptoms that arise from this disease include enlargement of the spleen, anemia, extreme fatigue and pain.

The estimated prevalence of MPNs suggest there are approximately 300,000 people living with the disease in the U.S., of which myelofibrosis accounts for approximately 18,000 patients. In Europe, there is a wide variation of prevalence observed across data sources. Myelofibrosis has a median age of 64 at the time of diagnosis and is a progressive disease with approximately 20 percent of patients eventually developing acute myeloid leukemia (AML). The median survival for high-risk myelofibrosis patients is less than 1.5 years, while the median survival for patients with myelofibrosis overall is approximately 6 years.

Forward-Looking Statements

This press release includes forward-looking statements, which are within the meaning of the Safe Harbor provisions of the Private Securities Litigation Reform Act of 1995. Such statements are subject to a number of risks and uncertainties, the outcome of which could materially and/or adversely affect actual future results and the trading price of CTI BioPharma's securities. Such statements include, but are not limited to, statements regarding expectations with respect to the potential important clinical benefits of pacritinib and the potential therapeutic utility of pacritinib. Investors are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this release. The statements are based on assumptions about many important factors and information currently available to us to the extent we have thus far had an opportunity to fully and carefully evaluate such information in light of all surrounding facts, circumstances, recommendations and analyses. A number of results and uncertainties could cause actual results to differ materially from those in the forward-looking statements, including those related to the satisfaction of regulatory and other requirements; the actions of regulatory bodies and other governmental authorities; changes in laws and regulations; other clinical trial results; that results observed to date may differ from future results or that different conclusions or considerations may qualify such results once existing data has been more fully evaluated; product quality, product efficacy, study protocol, data integrity or patient safety issues; product development risks; and other risks identified in each of the issuer's most recent filings on Forms 10-K and 10-Q and other Securities and Exchange Commission filings. Except as required by law, CTI BioPharma does not intend to update any of the statements in this press release upon further developments.

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