Kezar Life Sciences Reports Fourth Quarter and Year End 2020 Financial Results and Provides Business Updates KZR-616 clinical development in three severe autoimmune diseases is advancing with several data readouts expect

Kezar Life Sciences Reports Fourth Quarter and Year End 2020 Financial Results and Provides Business Updates

SOUTH SAN FRANCISCO, Calif.--(BUSINESS WIRE) - March 11, 2021 - Kezar Life Sciences, Inc. (Nasdaq: KZR), a clinical-stage biotechnology company discovering and developing breakthrough treatments for immune-mediated and oncologic disorders, today announced its fourth quarter and year end 2020 financial results and corporate highlights.

"Despite unprecedented circumstances, 2020 was a year of significant corporate and clinical accomplishments, thanks to the excellent execution by the Kezar team," said John Fowler, Kezar's Co-Founder and Chief Executive Officer. "We advanced our lead product candidate, KZR-616, in multiple indications, and the early clinical data from MISSION strongly support its continued development for a wide range of severe immune-mediated diseases. We launched the open-label extension study for patients completing PRESIDIO, and KZR-616 was granted Orphan Drug Designations from the FDA for the treatment of polymyositis and dermatomyositis. This year we look forward to reporting the final results of the MISSION Phase 1b study and interim data from the MISSION Phase 2 study in systemic lupus erythematosus and lupus nephritis patients, respectively."

Fowler continued, "Additionally, we continue to be highly encouraged by the therapeutic potential of KZR-261 and look forward to initiating a Phase 1 trial in solid tumors later this year. The data we'll be presenting from the protein secretion program in two posters during AACR next month provides further support for inhibiting Sec61 as a target to treat various cancers."

Clinical Highlights & Updates

KZR-616: Selective Immunoproteasome Inhibitor

MISSION - Phase 1b/2 clinical trial in patients with systemic lupus erythematous (SLE) and lupus nephritis (LN), respectively (NCT03393013)

PRESIDIO - Phase 2 clinical trial in patients with dermatomyositis (DM) and polymyositis (PM) (NCT04033926)

Protein Secretion Program

Poster Presentations

Title: Prioritizing tumor types for clinical study of novel Sec61 inhibitors by searching for expression profiles of sensitive cell lines in tumor sample databases

Presenter/s: Eric Lowe, R. Andrea Fan, Henry W. B. Johnson, Christopher J. Kirk, Dustin McMinn, Yu Qian, Brian Tuch

Session: Genomic Profiling of Tumors - Abstract #2226

Date and time: Available on demand [8:30AM ET, Saturday, April 10, 2021]

Title: Quantitative proteomic profiling of novel anti-cancer small molecule inhibitors of Sec61: Mechanistic investigation and biomarker discovery

Presenter/s: Yu Qian, Jennifer Whang, Janet Anderl, Andrea Fan, Henry W. B. Johnson, Christopher J. Kirk, Eric Lowe, Dustin McMinn, Beatriz Millare, Tony Muchamuel and Jinhai Wang; Kezar Life Sciences

Session: Proteomics and Biomarker Discovery - Abstract #2816

Date and time: Available on demand [8:30AM ET, Saturday, April 10, 2021]

KZR-616 is a novel, first-in-class, selective immunoproteasome inhibitor with broad therapeutic potential across multiple autoimmune diseases. Preclinical research demonstrates that selective immunoproteasome inhibition results in a broad anti-inflammatory response in animal models of several autoimmune diseases, while avoiding immunosuppression. Data generated from Phase 1a and 1b clinical trials provide evidence that KZR-616 exhibits a favorable safety and tolerability profile for development in severe, chronic autoimmune diseases. Phase 2 trials are underway in severe autoimmune diseases.

KZR-261, a novel, first-in-class protein secretion inhibitor, is the first clinical candidate to be nominated from Kezar's research and discovery efforts targeting protein secretion pathways. KZR-261 is a broad-spectrum anti-tumor agent that acts through direct interaction and inhibition of Sec61 activity. The compound was discovered by Kezar through a robust medicinal chemistry campaign in which several scaffolds were progressed through the company's proprietary platform evaluating Sec61 modulation. As a result, Kezar has established a broad library of protein secretion inhibitors. KZR-261 has demonstrated several encouraging properties that lead to its potential to be an anti-cancer agent for the treatment of solid and hematologic malignancies. An IND submission in solid tumors is expected to be filed in mid-2021.

About Lupus Nephritis

Lupus nephritis (LN) is one of the most serious complications of systemic lupus erythematosus (SLE). LN is a disease comprising a spectrum of vascular, glomerular, and tubulointerstitial lesions and develops in about 50% of SLE patients within 10 years of their initial diagnosis. LN is associated with considerable morbidity, including an increased risk of end-stage renal disease requiring dialysis or renal transplantation and an increased risk of death. There are limited approved therapies for the treatment of LN. Management typically consists of induction therapy to achieve remission and long-term maintenance therapy to prevent relapse.

About Dermatomyositis and Polymyositis

Polymyositis and Dermatomyositis are two of the five types of autoimmune myositis diseases. Both are chronic, debilitating, inflammatory autoimmune myopathies that are distinguished by inflammation of the muscles as well as the skin (in DM). An approximate 30,000-120,000 people in the United States are living with these severe and progressive inflammatory myopathies that are characterized by marked morbidity and associated mortality. While debilitating muscle weakness is the hallmark of these myopathies, including compromised muscles of respiration, other internal organ system dysfunctions can be equally disabling. The aim of treatment for these diseases is to suppress inflammation, increase muscle strength and prevent long-term damage to muscles and extramuscular organs; however, treatment options are limited for DM, and there are currently no approved treatments for PM.

About Kezar Life Sciences

Kezar Life Sciences is a clinical-stage biopharmaceutical company bringing novel treatments to patients with rare autoimmune diseases and cancer. The company is pioneering first-in-class, small-molecule therapies that harness master regulators of cellular function to inhibit multiple drivers of disease via single, powerful targets. KZR-616, its lead development candidate, is a selective immunoproteasome inhibitor being evaluated in Phase 2 clinical trials in lupus nephritis, dermatomyositis and polymyositis. Additionally, KZR-261, the first anti-cancer clinical candidate from the company's platform targeting the Sec61 translocon and the protein secretion pathway, is undergoing IND-enabling activities. For more information, visit www.kezarlifesciences.com.

Cautionary Note on Forward-looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Words such as "may," "will," "should," "expect," "believe" and similar expressions (as well as other words or expressions referencing future events, conditions or circumstances) are intended to identify forward-looking statements. These forward-looking statements are based on Kezar's expectations and assumptions as of the date of this press release. Each of these forward-looking statements involves risks and uncertainties that could cause Kezar's clinical development programs, future results or performance to differ materially from those expressed or implied by the forward-looking statements. Forward-looking statements contained in this press release include, but are not limited to, statements about the design, progress, timing, scope and results of clinical trials, the anticipated timing of disclosure of results of clinical trials, plans for initiating future clinical trials and extension studies, the likelihood data will support future development, the association of data with treatment outcomes, the likelihood of obtaining regulatory approval of Kezar's product candidates, the timing of regulatory filings, and the discovery and development of new product candidates. Orphan Drug Designation does not provide any assurance of regulatory approval or expedite regulatory review. Many factors may cause differences between current expectations and actual results, including the impacts of the COVID-19 pandemic on the company's business, clinical trials and financial position, unexpected safety or efficacy data observed during preclinical or clinical studies, clinical trial site activation or enrollment rates that are lower than expected, changes in expected or existing competition, changes in the regulatory environment, the uncertainties and timing of the regulatory approval process, and unexpected litigation or other disputes. Other factors that may cause actual results to differ from those expressed or implied in the forward-looking statements in this press release are discussed in Kezar's filings with the U.S. Securities and Exchange Commission, including the "Risk Factors" contained therein. Except as required by law, Kezar assumes no obligation to update any

forward-looking statements contained herein to reflect any change in expectations, even as new information becomes available.

SVP, Strategy & External Affairs