Principia Announces First Patient Dosed in Phase 2A Trial of Rilzabrutinib in IgG4-Related Disease

SOUTH SAN FRANCISCO, Calif., Sept. 17, 2020 (GLOBE NEWSWIRE) -- Principia Biopharma Inc. (Nasdaq: PRNB), a late-stage biopharmaceutical company focused on developing treatments for immune mediated diseases, today announced that the first patient was dosed in an open label two-arm trial to evaluate rilzabrutinib in IgG4-related disease (RD). 

“IgG4-RD is a serious fibro-inflammatory disease that can affect nearly any organ. The disease has long been under-diagnosed and under-treated, so we believe there is a significant medical need to have fast acting steroid free treatments with persistent responses. We believe rilzabrutinib has the potential to lead to positive outcomes in IgG4-RD by impacting many of the driving effector cells of the disease, including inflammatory monocytes, macrophages, eosinophils, B cells, IgG4+ plasmablasts and cytotoxic T-cells,” said Martin Babler, president and chief executive officer of Principia. 

About the Phase 2A Trial

This multicenter Phase 2A trial is anticipated to enroll approximately 25 patients with active IgG4-RD in two arms, rilzabrutinib with glucocorticoids or glucocorticoids only. Patients who meet all the inclusion criteria after completion of the four-week screening period will be randomized in a 3:1 ratio to the rilzabrutinib with glucocorticoids arm or the glucocorticoids only arm. The main treatment period is 12 weeks, and patients may then be eligible to enter a treatment extension period of 40 weeks, followed by a four-week safety follow-up period. The primary endpoint of the trial is the proportion of patients who achieve complete remission at week 12 with no glucocorticoid use at Week 4 for the rilzabrutinib arm and week 12 for the glucocorticoids arm.

About IgG4 Related Disease

There is significant need for new treatment options for patients with IgG4-RD. IgG4-RD is an immune-mediated disease of chronic inflammation and fibrosis that, if left untreated, can lead to severe morbidity including organ dysfunction and organ failure, which can be fatal. IgG4-related disease typically manifests with multiple organ involvement including but not limited to exocrine glands, GI tract organs (liver, pancreas), and kidneys.

Treatment is typically glucocorticoids (GCs); however, patients often relapse after GCs are tapered and thus require chronic GC dosing, which can lead to severe and debilitating side effects. Rituximab has been shown to have an effective clinical response; however, patients frequently relapse after treatment as well. Recent advances in the field have led to recognition of this disease and the many unmet needs for the patients diagnosed with it. Awareness and recognition of IgG4-RD is growing, and the exact prevalence remains unknown, with estimates ranging from 40,000 to 180,000 in the United States alone.

About Rilzabrutinib

Rilzabrutinib, Principia’s most advanced drug candidate, is an oral, first-in-class, reversible covalent, Bruton tyrosine kinase (BTK) inhibitor optimized for the treatment of immune mediated diseases. BTK is involved in innate and adaptive immune responses and is a critical signaling molecule in immune mediated diseases. Rilzabrutinib data demonstrates an ability to block inflammatory immune cells, eliminate autoantibody destructive signaling, and prevent new autoantibody production without depleting B cells. Rilzabrutinib’s unique attributes are based in the power of the bond from Principia’s proprietary Tailored Covalency® platform.  This enabled the company to optimize rilzabrutinib’s safety and efficacy profile, with prolonged and reversible action at the target site while being rapidly eliminated from the body. Principia believes this bonding and the limited systemic exposure of rilzabrutinib enables rapid clinical reversibility of effects on the immune system, and it is thus designed for safety in immune mediated diseases. 

About Principia Biopharma

Principia is a late-stage biopharmaceutical company dedicated to bringing transformative therapies to patients with significant unmet medical needs in immune mediated diseases. Through Principia’s proprietary Tailored Covalency® platform, our strategy is to build and advance a pipeline of best-in-class drug candidates with significant therapeutic benefits, limit unintended side effects, improve quality of life and over time modify the course of disease. This highly reproducible approach enables the company to pursue multiple programs efficiently, having discovered three drug candidates. Rilzabrutinib, a reversible covalent BTK inhibitor, is being evaluated in a global Phase 3 clinical trial in pemphigus, a Phase 1/2 clinical trial in immune thrombocytopenia (ITP), a Phase 2A clinical trial in IgG4-RD and the company plans to initiate a Phase 3 trial in ITP. PRN2246/SAR442168 is a covalent BTK inhibitor which crosses the blood-brain barrier and is licensed to Sanofi. Sanofi has announced that SAR442168 has entered Phase 3 clinical trials in multiple sclerosis. PRN473 Topical, a topical reversible covalent BTK inhibitor designed for immune-mediated diseases that could benefit from localized application to the skin, is being evaluated in Phase 1 trials.  For more information, please visit

Forward-Looking Statements

This press release contains forward-looking statements. Forward-looking statements are statements that are not historical facts and may include projections and estimates and their underlying assumptions, statements regarding plans, objectives, intentions and expectations with respect to future financial results, events, operations, services, product development and potential plans, and future performance, including, but not limited to, Principia’s expectations regarding the Principia pipeline of product candidates, the design of, progress of (including the anticipated enrollment for its Phase 2A trial in IgG4-RD), results from, and timing of, its clinical trials and information regarding the timing, scope and success of additional clinical results. Forward-looking statements are generally identified by the words “expects”, “anticipates”, “believes”, “intends”, “estimates”, “plans”, “will be” and similar expressions. Although Principia management believes that the expectations reflected in such forward-looking statements are reasonable, investors are cautioned that forward-looking information and statements are subject to various risks and uncertainties, many of which are difficult to predict and generally beyond the control of Principia, that could cause actual results and developments to differ materially from those expressed in, or implied or projected by, the forward-looking information and statements. These risks and uncertainties include among other things, risks relating to the ability to complete and the timing of completion of the transactions contemplated by the Agreement and Plan of Merger (the “Merger Agreement”) Principia entered into on August 16, 2020, with Sanofi and Kortex Acquisition Corp. (“Purchaser”), a wholly owned subsidiary of Sanofi, including the parties’ ability to satisfy the conditions to the consummation of the tender offer (the “Offer”) and the other conditions set forth in the Merger Agreement, the risk that stockholder litigation in connection with the proposed transaction may result in significant costs and the possibility of any termination of the Merger Agreement; the uncertainties inherent in research and development, including future clinical data and analysis, regulatory obligations and oversight by regulatory authorities, such as the FDA, and risks associated with Principia’s intellectual property. The forward-looking statements contained in this communication are based on current expectations and assumptions that are subject to risks and uncertainties which may cause actual results to differ materially from the forward-looking statements. Actual results may differ materially from current expectations because of risks associated with uncertainties as to the timing of the Offer and the merger contemplated by the Merger Agreement (the “Merger”); the risk that competing offers or acquisition proposals will be made; the possibility that various conditions to the consummation of the Offer or the Merger may not be satisfied or waived, including that a governmental entity may prohibit, delay or refuse to grant approval for the consummation of the Offer or the Merger; the effects of disruption from the transactions of Principia’s business and the fact that the announcement and pendency of the transactions may make it more difficult to establish or maintain relationships with employees or vendors. The risks and uncertainties may be amplified by the COVID-19 pandemic, which has caused significant economic uncertainty. The extent to which the COVID-19 pandemic impacts Principia’s businesses, operations, and financial results, including the duration and magnitude of such effects, will depend on numerous factors, which are unpredictable, including, but not limited to, the duration and spread of the outbreak, its severity, the actions to contain the virus or treat its impact, and how quickly and to what extent normal economic and operating conditions can resume. While the list of factors presented here is representative, no list should be considered a statement of all potential risks, uncertainties or assumptions that could have a material adverse effect on the companies’ consolidated financial condition or results of operations. The foregoing factors should be read in conjunction with the risks and cautionary statements discussed or identified in Principia’s public filings with the SEC from time to time, including Principia’s most recent Annual Report on Form 10-K for the year ended December 31, 2019, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K. Principia’s stockholders and investors are cautioned not to unduly rely on these forward-looking statements. The forward-looking statements speak only as of the date hereof and, other than as required by applicable law, Principia does not undertake any obligation to update or revise any forward-looking information or statements.

Additional Information and Where to Find It

In connection with the proposed acquisition of Principia by Sanofi, Purchaser commenced a tender offer for all of the outstanding shares of Principia on August 28, 2020. This communication is for informational purposes only and is neither an offer to purchase nor a solicitation of an offer to sell shares of Principia nor is it a substitute for the tender offer materials that Sanofi and Purchaser filed with the upon commencement of the tender offer. On August 28, 2020, Sanofi and Purchaser filed tender offer materials on Schedule TO with the SEC and Principia filed a Solicitation/Recommendation Statement on Schedule 14D-9 with the SEC with respect to the offer. The tender statement on Schedule TO, the offer to purchase, the Solicitation/Recommendation Statement of Principia on Schedule 14D-9 and related materials with respect to the tender offer and the merger are available to Principia’s stockholders free of charge at the website of the SEC at or from the information agent named in the tender offer materials. Investors may also obtain, at no charge, the documents filed with or furnished to the SEC by Principia under the “Investors and Media” section of Principia’s website at www.principiabio. Principia’s stockholders are advised to read the tender offer statement and the solicitation/recommendation statement and any amendments thereto, as well as any other documents relating to the tender offer and the merger that are filed with the SEC, carefully and in their entirety prior to making any decisions with respect to whether to tender their shares into the tender offer because they contain important information, including the terms and conditions of the tender offer.

In addition to the Solicitation/Recommendation Statement that Principia has filed, Principia files annual, quarterly and current reports, proxy statements and other information with the SEC. You may read and copy any reports, statements or other information filed by Principia at the SEC public reference room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information on the public reference room. Principia’s filings with the SEC are also available to the public from commercial document-retrieval services and the SEC’s website at



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