CTI BioPharma Presents Data from Pacritinib Program at the 63rd American Society of Hematology Meeting

SEATTLE, Dec. 13, 2021 /PRNewswire/ -- CTI BioPharma Corp. (Nasdaq: CTIC) announced five scientific poster presentations on the pacritinib clinical program at the 63^rd American Society of Hematology (ASH) Annual Meeting & Exposition, being held as a hybrid (virtual and live) meeting in Atlanta, Georgia, December 11-14, 2021.

"We are pleased with the growing body of clinical evidence supporting the potential of pacritinib's unique place in treating cytopenic myelofibrosis, specifically in patients with moderate or severe thrombocytopenia, a notable challenge in light of the significant limitations of approved therapies," said Adam R. Craig, M.D., Ph.D., President and Chief Executive Officer of CTI BioPharma. "Importantly, today we presented data demonstrating that in patients with cytopenic myelofibrosis, full-dose pacritinib yielded higher response rates and a similar safety profile to lower doses of ruxolitinib. Prolonged administration of pacritinib is possible with favorable tolerability in the compassionate use setting, and the use of pacritinib can lead to significant overall and individual symptom relief in patients with both moderate and severe thrombocytopenia."

"As we approach our PDUFA action date of February 28, 2021, we remain focused on bringing forward a new therapeutic option for patients with cytopenic myelofibrosis through our committed collaboration with the FDA."

All presentation materials will be available at ctibiopharma.com.

A Retrospective Head-to-Head Comparison between Pacritinib and Ruxolitinib in Patients with Myelofibrosis and Moderate to Severe Thrombocytopenia (ASH Poster #3639)

Pacritinib, a JAK 2/interleukin-1 receptor–associated kinase 1 (IRAK1) inhibitor that does not inhibit JAK1, is in development for use in patients with myelofibrosis who have thrombocytopenia. Pacritinib was studied in thrombocytopenic patients (platelet count ≤100 x 10⁹/L) in the randomized phase 3 PERSIST-2 trial, which showed pacritinib was superior to best available therapy (BAT), including ruxolitinib, based on spleen volume reduction (SVR) and modified total symptom score (mTSS) response. While many patients in the BAT arm (45%) received ruxolitinib, an analysis of the comparison between pacritinib and ruxolitinib has not been previously performed.

This retrospective head-to-head analysis of pacritinib versus ruxolitinib in "first-line" (ruxolitinib-naïve) patients treated in PERSIST-2 showed that patients with moderate or severe thrombocytopenia were able to maintain full dose intensity with pacritinib. Pacritinib fully dosed at 400 mg/day resulted in numerically higher rates of SVR (28% vs 11%) and mTSS response (37% vs 11%), and a similar safety profile compared with lower doses of ruxolitinib in "first-line" patients with cytopenic myelofibrosis, suggesting that pacritinib may address the unmet medical need of patients with cytopenic myelofibrosis who cannot tolerate full doses of JAK1/2 inhibitors, such as ruxolitinib.

Safety Analysis of Pacritinib in Patients with Myelofibrosis and Severe Thrombocytopenia (ASH Poster #3640)

Pacritinib, a novel JAK2/IRAK1 inhibitor, demonstrated clinically significant activity in spleen volume and symptom reduction in patients with advanced cytopenic myelofibrosis, including those with severe thrombocytopenia (platelet count <50 x 10⁹/L), in phase 2 and 3 clinical trials. Pacritinib, unlike JAK1/2 inhibitors, has demonstrated clinical benefit at the recommended full dose of 200 mg twice daily (BID) in patients with cytopenias in the phase 2 dose–finding PAC203 and phase 3 PERSIST-2 trials.

In this retrospective safety analysis of patients with cytopenic myelofibrosis, including those who had severe thrombocytopenia, the safety profile of pacritinib 200 mg BID was comparable to best available therapy (BAT), which included non-therapeutic options (i.e. supportive care and watch and wait). This analysis suggests that pacritinib 200 mg BID may represent the first fully dosed therapeutic option for patients with cytopenic myelofibrosis, including severe thrombocytopenia.

Long-Term Treatment with Pacritinib on a Compassionate Use Basis in Patients with Advanced Myelofibrosis (ASH Poster #3649)

The efficacy and safety of pacritinib has been evaluated in multiple clinical trials, including two randomized, controlled phase 3 trials (PERSIST-1 and PERSIST-2) and a phase 2 dose-finding trial (PAC203). These trials are unique in the myelofibrosis landscape because they enrolled patients with advanced disease and severe cytopenias. When these trials closed, patients who received pacritinib could apply to continue treatment on a compassionate use basis. This analysis describes pacritinib treatment in this program. 

Patients who were treated with pacritinib on PERSIST-1, PERSIST-2, or PAC203 were provided the option to continue receiving pacritinib if they were eligible for the compassionate use program. After receiving pacritinib on an original clinical trial, 75 patients continued to receive pacritinib on a compassionate use basis. Twenty patients were still on pacritinib as of the data cutoff date. Most patients had advanced disease, characterized by cytopenias and circulating blasts.

Median total combined treatment duration (original trial and compassionate use) was 21.1 months (range 0.8 to 80.9 months). Among patients with prior JAK inhibitor exposure, median time from discontinuation from a JAK inhibitor to the last day of known treatment with compassionate use pacritinib was 27.2 months. This duration compares favorably to median survival reported in patients discontinuing ruxolitinib: 14 months overall and about 8 months if the platelet count is <100×10⁹/L.. Prolonged treatment with pacritinib is well-tolerated in patients with advanced myelofibrosis, including those with cytopenias, and reported serious adverse events were consistent with those expected in advanced myelofibrosis patient population and with treatment in a compassionate use setting.

The Impact of Pacritinib on Myelofibrosis Symptoms in Patients with Moderate and Severe Thrombocytopenia: A Retrospective Analysis of Patients in the Persist-2 Trial (ASH Poster #3628)

Pacritinib demonstrated superior spleen volume response versus BAT in patients with myelofibrosis who have moderate or severe thrombocytopenia (platelet count ≤100 x 10⁹/L) in the phase 3 PERSIST-2 trial. Unlike the trials in which JAK1/2 inhibitors were approved, which relied on a modified TSS (mTSS) score that excluded "tiredness," PERSIST-2 included tiredness as part of the TSS.

This retrospective analysis showed that significantly more patients achieved a mTSS response with pooled pacritinib versus BAT (31% vs 14%; P=0.008). More patients achieved a mTSS response with pacritinib 200 mg BID versus BAT (35% vs 14%; P=0.004) and BAT=RUX (35% vs 19%; P=0.110). Patients in the pacritinib 200 mg BID arm experienced greater percent reductions in individual myelofibrosis symptoms between baseline and week 24 compared with BAT, and the severity of physical function symptoms were reduced more with pacritinib 200 mg BID compared with BAT by week 24.

Evidence of NF-ΚB Pathway Activation in Patients with Advanced, High Molecular Risk Myelofibrosis (ASH Poster #3584)

Patients with myelofibrosis who discontinue treatment with ruxolitinib have a poor prognosis that is often associated with advanced phases of disease and severe cytopenias. While these patients are more likely to have high molecular risk (HMR) genomic markers, biological drivers of disease in this advanced population are not well characterized. The interaction between high-risk mutations and cytokine profiles of patients treated in PAC203 were retrospectively analyzed.

In this HMR+ and RAS mutant-enriched cohort of myelofibrosis patients who were intolerant of or resistant to ruxolitinib, a relationship between HMR mutations and an NF-kB directed pro-inflammatory cytokine signature was identified. These results implicate the activation of a distinct biological signaling pathway operative in this molecularly-defined cohort.

About Myelofibrosis and Cytopenias
Myelofibrosis is a bone marrow cancer that results in the formation of fibrous scar tissue and can lead to thrombocytopenia and anemia, weakness, fatigue and an enlarged spleen and liver. Within the U.S. there are approximately 21,000 patients with myelofibrosis, 7,000 of which have severe thrombocytopenia (defined as blood platelet counts of less than 50 x10⁹/L). Severe thrombocytopenia is associated with poor survival and high symptom burden and can occur as a result of disease progression or from drug toxicity with other JAK2 inhibitors such as JAKAFI and INREBIC.

About Pacritinib
Pacritinib is an investigational oral kinase inhibitor with specificity for JAK2, IRAK1 and CSF1R, but not JAK1. 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 FLT.

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 developing and commercializing pacritinib, our product candidate currently in active late-stage development. We are headquartered in Seattle, Washington.

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 and 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: FDA review timelines and the ultimate outcome of the FDA review of our NDA for pacritinib; our ability to successfully demonstrate the safety and efficacy of pacritinib; the risk that the FDA may determine that the benefit/risk profile of pacritinib at the dose selected for the PACIFICA phase 3 trial does not support approval; the risk that pacritinib may be delayed to a point where it is not commercially viable; 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. "CTI BioPharma" and the CTI BioPharma logo are registered trademarks or trademarks of CTI BioPharma Corp. in various jurisdictions. All other trademarks belong to their respective owner.

CTI BioPharma Investor Contacts:
Argot Partners
+212-600-1902
[email protected]

SOURCE CTI BioPharma Corp.

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