Protagonist Therapeutics Presents Updated Phase 2 Rusfertide Data in Polycythemia Vera (PV) at ASH 2021 Annual Meeting

NEWARK, Calif., Dec. 12, 2021 /PRNewswire/ -- Protagonist Therapeutics (Nasdaq: PTGX) ("Protagonist" or "the Company") today presented updated data from two ongoing Phase 2 studies evaluating rusfertide in patients with polycythemia vera (PV), demonstrating its ability to essentially eliminate the need for phlebotomies in patients. Rusfertide also showed rapid and sustained hematocrit control in patients requiring frequent phlebotomies or those having high baseline hematocrit levels (>48%). The data were presented in two oral presentations at the American Society of Hematology (ASH) 2021 Annual Meeting, in addition to the Company's three poster presentations: one describing the Phase 3 study design for rusfertide in PV; one presenting pre-clinical findings with a hepcidin analog in a mouse model of PV; and another poster on the Phase 2 clinical proof-of-concept data for rusfertide in hereditary hemochromatosis (HH).

"The latest data continues to demonstrate rusfertide's potential to maintain rapid and durable control of hematocrit and essentially eliminate the need for phlebotomies in phlebotomy-dependent PV patients, while offering meaningful improvements across various quality of life measures," said Ronald Hoffman, MD, Director of the Myeloproliferative Disorders Research Program at the Icahn School of Medicine at Mount Sinai, and principal investigator for the study. "Early findings for rusfertide induction therapy also demonstrate its ability to rapidly control hematocrit in patients with elevated hematocrit levels above 48 percent, and to sustain those effects in maintenance, highlighting rusfertide's potential efficacy in a wider spectrum of PV patients."

"We are extremely encouraged by the totality and consistency of the positive results presented today at ASH for rusfertide in polycythemia vera, and by the support we are garnering from the physician community as we continue to execute against our goal of addressing unmet medical needs through this natural hormone mimetic therapy," said Dinesh V. Patel, PhD, President and Chief Executive Officer of Protagonist. "The upcoming double-blinded, placebo-controlled Phase 3 PV study is a transformative step in the progressive journey of rusfertide, from de novo discovery to a registrational study. In addition, we look forward to providing clarity on our next steps in HH and other iron-overload related diseases in 2022, thereby expanding the potential utility of rusfertide into multiple indications."

Summary of Key Results

Updated Results from Phase 2 Study Evaluating Rusfertide in Patients with PV

In this Phase 2 study, 63 phlebotomy-dependent PV patients were treated with rusfertide for up to 18 months. The results of the study demonstrated the essential elimination of the need for therapeutic phlebotomy (TP). Rapid, sustained, and durable control of hematocrit levels below 45% was observed without a significant increase in white blood cell numbers or PV-related thromboses. During the first 28 weeks on treatment, 84% of patients required no phlebotomies, 14% required one, and 2% required two phlebotomies. The most frequent adverse events were injection site reactions which were transient in nature. Importantly, none of the treated PV patients suffered from thrombotic events. Serious and Grade 3-4 events were limited in number, less than 10 at the time of data cut-off. Two SAEs were previously reported as possible related to study drug.

Among patient reported outcomes, a third of the patients in the study also saw at least a 40% reduction in Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Scores (MPN-SAF-TSS) from baseline at week 28. Sixty-nine percent of patients reported improvement in Patient Global Impression of Change from baseline at week 8.

New Results from Phase 2 Study Evaluating Rusfertide as an Induction Therapy in Patients with PV

In this Phase 2 study, induction therapy with twice weekly rusfertide was administered alone to patients with confirmed high hematocrit levels above 48%.  In all 16 erythrocytotic PV patients, rusfertide demonstrated rapid reduction of hematocrit below 45% within weeks, without the need for TP. The drug was well tolerated. Post-induction, weekly rusfertide treatment maintained hematocrit levels without the need for TP. While this study remains ongoing, most reported drug related adverse events to date were grade 1-2, with injection site reactions being the most common adverse event.

Additional Poster Presentations

The design of Protagonist's planned three-part, multicenter, global, double-blinded, placebo-controlled Phase 3 clinical trial was presented in a poster. This Phase 3 study is expected to commence in Q1 2022 and will evaluate rusfertide in patients with PV compared to placebo when added onto current therapy. The primary endpoint of the study will be the absence of phlebotomy during weeks 20-32 for patients on rusfertide.

Also presented in a poster were results from a pre-clinical study demonstrating that a rusfertide peptide analog reduced erythrocytosis by restricting iron needed for red blood cell production while normalizing body iron distribution in a murine model with JAK2-V617F mutations. These effects support the use of a hepcidin mimetic, such as rusfertide, for potential utility in PV through dose titration treatment to maintain hematocrit below 45%.

Results from a Phase 2a proof-of-concept study evaluating rusfertide in patients with HH were also presented in a poster, demonstrating that rusfertide reduced serum iron and maintained transferrin saturation below 45% with corresponding significant reductions in phlebotomies. Liver iron concentration measured by MRI were also maintained at pre-study levels in patients at the end of the six-month study. Rusfertide was generally well tolerated in patients with HH, with the most common adverse events being injection site reactions that were mild or moderate. 

Details for ASH 2021 presentations are as follows:

Oral Presentations

Title: "Rusfertide (PTG-300) Controls Hematocrit Levels and Essentially Eliminates Phlebotomy Requirement in Polycythemia Vera Patients"
Session Title: 634. Myeloproliferative Syndromes: Clinical and Epidemiological: Novel Therapies for MPNs and JAK inhibitors for Myelofibrosis
Authors: Ronald Hoffman, MD, et al.

Title: "Rusfertide (PTG-300) Induction Therapy Rapidly Achieves Hematocrit Control in Polycythemia Vera Patients without the Need for Therapeutic Phlebotomy"
Session Title: 634. Myeloproliferative Syndromes: Clinical and Epidemiological: Novel Therapies for MPNs and JAK inhibitors for Myelofibrosis
Authors: Yelena Ginzburg, MD, et al.

Posters

Title: "A Phase 3 Study of the Hepcidin Mimetic Rusfertide (PTG-300) in Patients with Polycythemia Vera"
Session Title: 634. Myeloproliferative Syndromes: Clinical and Epidemiological: Poster I
Authors: Srdan Verstovsek, MD, PhD, et al.

Title: "Regulation of Iron Homeostasis and Efficacy of Rusfertide Analog Peptide in a Mouse Model for Polycythemia Vera"
Session Title: 102. Iron Homeostasis and Biology: Poster II
Authors: Roopa Taranath, PhD, et al.

Title: "Rusfertide (PTG-300), a Hepcidin Mimetic, Maintains Liver Iron Concentration in the Absence of Phlebotomies in Patients with Hereditary Hemochromatosis"
Session Title: 102. Iron Homeostasis and Biology: Poster I
Authors: Kris V. Kowdley, MD, et al.

About Protagonist

Protagonist Therapeutics is a biopharmaceutical company with multiple peptide-based investigational new chemical entities (NCEs) in different stages of development, all derived from the Company's proprietary technology platform.

Protagonist's pipeline includes rusfertide (PTG-300), an investigational, injectable hepcidin mimetic currently in a Phase 2 proof-of-concept clinical trial for polycythemia vera (PV), a Phase 2 study in PV subjects with high hematocrit levels, and a recently completed Phase 2a study for hereditary hemochromatosis. The Company plans to initiate a single, global Phase 3 randomized, placebo-controlled trial evaluating the efficacy and safety of a once weekly, subcutaneously self-administered dose of rusfertide.

The Company is also evaluating an orally delivered, gut-restricted alpha-4-beta-7 integrin specific antagonist peptide (PN-943) currently in a Phase 2 study in adults with moderate to severe active ulcerative colitis (UC). The Company is targeting ulcerative colitis as the initial indication.

The Company has a worldwide license and collaboration agreement with Janssen Biotech, Inc., for the development of oral peptide IL-23 receptor antagonist PN-235, a second-generation oral interleukin-23 receptor antagonist candidate. Under the collaboration with Janssen, PN-235 is expected to advance into Phase 2 studies in psoriasis and new Phase 2 clinical studies in inflammatory bowel diseases.

Cautionary Note on Forward-Looking Statements

This press release contains forward-looking statements for purposes of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Forward-looking statements include statements regarding our intentions or current expectations concerning, among other things, the Company's clinical development program for rusfertide in PV, and the potential benefits of rusfertide in PV patients. In some cases, you can identify these statements by forward-looking words such as "anticipate," "believe," "may," "will," "expect," or the negative or plural of these words or similar expressions. Forward-looking statements are not guarantees of future performance and are subject to risks and uncertainties that could cause actual results and events to differ materially from those anticipated, including, but not limited to, our ability to develop and commercialize our product candidates, our ability to earn milestone payments under our collaboration agreements, the impact of the current COVID-19 pandemic on our discovery and development efforts, our ability to use and expand our programs to build a pipeline of product candidates, our ability to obtain and maintain regulatory approval of our product candidates, our ability to operate in a competitive industry and compete successfully against competitors that have greater resources than we do, and our ability to obtain and adequately protect intellectual property rights for our product candidates.  Additional information concerning these and other risk factors affecting our business can be found in our periodic filings with the Securities and Exchange Commission, including under the heading "Risk Factors" contained in our most recently filed periodic reports on Form 10-K and Form 10-Q filed with the Securities and Exchange Commission. Forward-looking statements are not guarantees of future performance, and our actual results of operations, financial condition and liquidity, and the development of the industry in which we operate, may differ materially from the forward-looking statements contained in this press release.  Any forward-looking statements that we make in this press release speak only as of the date of this press release. We assume no obligation to update our forward-looking statements, whether as a result of new information, future events or otherwise, after the date of this press release.

SOURCE Protagonist Therapeutics, Inc.

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