Exhibit 99.1

Principia Biopharma Reports Second Quarter 2020

Financial Results

SOUTH SAN FRANCISCO, Calif., August 6, 2020 – Principia Biopharma Inc. (Nasdaq: PRNB), a late-stage biopharmaceutical company focused on developing treatments for immune mediated diseases, today announced financial results for the second quarter ended June 30, 2020.

“We are very pleased with the progress the company made on each program in the first half of the year despite the ongoing COVID-19 pandemic challenges. Our investigators were able to present additional positive data for both ITP and pemphigus and Sanofi announced positive Phase 2 data in multiple sclerosis,” said Martin Babler, president and chief executive officer of Principia. “With the initiation of a Phase 3 trial in patients with relapsing multiple sclerosis, we received a $50 million milestone payment from Sanofi which enhances our balance sheet and allows us to continue strong execution on our programs.”

Six-month and year-to date program highlights

Second Quarter 2020 Financial Results

Cash Position: Cash, cash equivalents, and marketable securities were $316.5 million as of June 30, 2020, compared to $367.8 million as of December 31, 2019. In addition, the company received an additional $50.0 million milestone payment from Sanofi in the third quarter of 2020.

Revenues: Collaboration revenues were $50.0 million for the three months ended June 30, 2020, compared to $30.0 million for the same period in 2019, for the achievement of clinical development milestones in our Sanofi collaboration.

R&D Expenses: Total research and development expenses were $30.9 million for the three months ended June 30, 2020, including stock-based compensation expense of $3.9 million, compared to $18.7 million for the same period in 2019, including stock-based compensation expense of $1.8 million. The increase in total research and development expenses was mainly driven by an increase in rilzabrutinib program costs, due to the progression of our global Phase 3 trial in pemphigus, ongoing Phase 2 trial in ITP and certain

manufacturing campaigns to supply drug products for our rilzabrutinib clinical trials, the initiation of our Phase 1 trial for PRN473 Topical in March 2020 and an increase in employee-related expenses.

G&A Expenses: General and administrative expenses were $9.2 million for the three months ended June 30, 2020, including stock-based compensation expense of $3.1 million, compared to $5.2 million for the same period in 2019, including stock-based compensation expense of $1.7 million.  The increase in total general and administrative expenses was primarily driven by increased employee-related expenses and costs related to operating as a public company.

Net Income (Loss): For the three months ended June 30, 2020, net income was $10.8 million compared to net income of $7.1 million for the same period in 2019.

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 participants with pemphigus, a Phase 1/2 clinical trial in participants with immune thrombocytopenia (ITP), and the company plans to initiate a Phase 2 clinical trial in participants with IgG4-Related Diseases and a Phase 3 trial in ITP. PRN2246/SAR442168 is a covalent BTK inhibitor which crosses the blood-brain barrier and is partnered with Sanofi.  Sanofi has announced that SAR442168 will be evaluated in four Phase 3 clinical trials in participants with relapsing and progressive forms of 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 www.principiabio.com.

Forward-Looking Statements

This press release contains forward-looking statements. These forward-looking statements reflect the current beliefs and expectations of management made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995, including, but not limited to, Principia’s expectations regarding the Principia pipeline of product candidates, and the initiation, timing, scope and success of additional clinical trials and results. Such forward-looking statements involve known and unknown risks, uncertainties, and other important factors that may cause Principia’s actual results, performance, or achievements to be materially different from those expressed or implied by the forward-looking statements. For a description of the risks and

uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to Principia’s business in general, see the risk factors set forth in Principia’s reports filed with the Securities and Exchange Commission. Any forward-looking statements contained in this press release speak only as of the date hereof, and Principia specifically disclaims any obligation to update any forward-looking statement, whether as a result of new information, future events or otherwise.

Investor Contact
Christopher Chai, CFO
ir@principiabio.com

Media Contact
Paul Laland
415.519.6610
media@principiabio.com

Principia Biopharma Inc.

Condensed Consolidated Statements of Operations

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(In thousands, except share and per share amounts)

Principia Biopharma Inc.

Summary Consolidated Balance Sheet Data

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