Phase 1 Trial Demonstrates Encouraging Clinical Benefit and Promising Safety Profile of Pacritinib for the Prevention of Graft-Versus-Host Disease Published in Clinical Cancer Research

SEATTLE, March 22, 2021 /PRNewswire/ --CTI BioPharma Corp. (Nasdaq: CTIC), today announced that Clinical Cancer Research, a journal of the American Association for Cancer Research, has published results from a Phase 1 study led by Joseph Pidala, MD, PhD (Moffitt Cancer Center), and Brian C. Betts, MD (Masonic Cancer Center at the University of Minnesota), evaluating pacritinib, an investigational oral kinase inhibitor with specificity for JAK2, for the prevention of acute graft-versus-host disease (GVHD). The results demonstrated that pacritinib, combined with sirolimus and low-dose tacrolimus (PAC/SIR/TAC), has a promising safety profile and exhibits preliminary therapeutic activity in preventing acute GVHD after allogeneic hematopoietic cell transplantation. The article, titled “Pacritinib Combined with Sirolimus and Low-Dose Tacrolimus for GVHD Prevention after Allogeneic Hematopoietic Cell Transplantation: Preclinical and Phase 1 Trial Results,” is available online (http://clincancerres.aacrjournals.org/content/early/2021/03/17/1078-0432.CCR-20-4725). The Phase 2 portion of the trial (NCT02891603) designed to evaluate the therapeutic effect of pacritinib in combination with sirolimus and low-dose tacrolimus for GVHD prevention is ongoing at Moffitt Cancer Center and the Masonic Cancer Center at the University of Minnesota.

The Phase 1 portion of the trial (NCT02891603) evaluated the safety of pacritinib when administered with sirolimus plus low-dose tacrolimus after allogeneic hematopoietic cell transplantation (alloHCT). A 3+3 dose escalation design identified PAC 100 mg twice a day as the minimum biologically active and well-tolerated dose for further study. At this dose, one out of six study participants treated with the investigational regimen had Grade 2-4 acute GVHD. Chronic GVHD was rare, with only two participants developing mild disease per NIH consensus criteria, which resolved without systemic immune suppression.

The new manuscript reports that dual JAK2/mTOR inhibition suppresses pathogenic Th1 and Th17 cells, enhances the potency of immunosuppressive regulatory T cells (Tregs), and maintains natural killer cells and CD8⁺ cytotoxic T lymphocytes required for graft-versus-leukemia. Importantly, PAC/SIR/TAC was observed to preserve donor cytomegalovirus (CMV) immunity, permit timely engraftment, and avoid cytopenias observed with nonselective JAK inhibitors.

“The PAC/SIR/TAC regimen provides concurrent inhibition of JAK2 and mTOR, effectively suppressing donor T cell costimulation and IL-6 signal transduction implicated in acute GVHD, while sparing STAT5 activation critical for immune tolerance and donor anti-leukemia immunity,” said Brian C. Betts, MD, Associate Professor of Medicine in the Division of Hematology, Oncology, and Transplantation at the University of Minnesota. “The favorable safety profile to date and its impact on immune reconstitution after alloHCT make the PAC/SIR/TAC regimen a promising strategy to prevent GVHD. We are excited to continue to investigate the use of pacritinib in this important area of unmet need.”

“This Phase 1 clinical trial is the first study to demonstrate that combining pacritinib, a selective JAK2 inhibitor, with sirolimus-based GVHD prophylaxis may produce lower rates of acute GVHD compared to the reported rates for sirolimus and tacrolimus alone,” said Adam. R. Craig, MD, PhD, President and Chief Executive Officer of CTI BioPharma. “We are encouraged by these data and look forward to further evaluating pacritinib in preventing GVHD in the on-going Phase 2 clinical trial and continuing to highlight the potential for the expanded use of pacritinib.”

About Pacritinib
Pacritinib is an investigational oral kinase inhibitor with specificity for JAK2, 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 CTI BioPharma Corp.
We are a biopharmaceutical company focused on the acquisition, development, and commercialization of novel targeted therapies for blood-related cancers that offer a unique benefit to patients and their healthcare providers. We concentrate our efforts on treatments that target blood-related cancers where there is an unmet medical need. In particular, we are focused on evaluating pacritinib, our sole product candidate currently in active late-stage development, for the treatment of adult patients with myelofibrosis. In addition, we have recently started developing pacritinib for use in hospitalized patients with severe COVID-19, in response to the COVID-19 pandemic. We are headquartered in Seattle, Washington.

About the Masonic Cancer Center, University of Minnesota
The Masonic Cancer Center, University of Minnesota, is the Twin Cities’ only Comprehensive Cancer Center, designated ‘Outstanding’ by the National Cancer Institute. As Minnesota’s Cancer Center, we have served the entire state for more than 25 years. Our researchers, educators, and care providers have worked to discover the causes, prevention, detection, and treatment of cancer and cancer-related diseases. Learn more at cancer.umn.edu.

About Moffitt Cancer Center
Moffitt is dedicated to one lifesaving mission: to contribute to the prevention and cure of cancer. The Tampa-based facility is one of only 51 National Cancer Institute-designated Comprehensive Cancer Centers, a distinction that recognizes Moffitt’s scientific excellence, multidisciplinary research, and robust training and education. Moffitt is the No. 11 cancer hospital and has been nationally ranked by U.S. News & World Report since 1999. Moffitt’s expert nursing staff is recognized by the American Nurses Credentialing Center with Magnet^® status, its highest distinction. With more than 7,000 team members, Moffitt has an economic impact in the state of $2.4 billion. For more information, call 1-888-MOFFITT (1-888-663-3488), visit MOFFITT.org, and follow the momentum on Facebook, Twitter, Instagram and YouTube.

CTI BioPharma Forward-Looking Statements
Statements included in this press release that are not historical in nature are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, Section 21E of the Securities Exchange Act of 1934 and the Private Securities Litigation Reform Act of 1995. These forward-looking statements are based on current assumptions that involve risks, uncertainties and other factors that may cause the actual results, events or developments to be materially different from those expressed or implied by such forward-looking statements. These risks and uncertainties include, but are not limited to: our ability to successfully demonstrate the safety and efficacy of pacritinib in various indications across multiple clinical trials; and those risks more fully discussed in the section entitled “Risk Factors” in our Annual Report on Form 10-K for the year ended December 31, 2020 and subsequent quarterly reports on Form 10-Q. These forward-looking statements speak only as of the date hereof and we assume no obligation to update these forward-looking statements, and readers are cautioned not to place undue reliance on such forward-looking statements.

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CTI BioPharma Investor Contacts:
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