Vor Bio Doses First Patient in Global Phase 3 UPSTREAM SjD Registrational Trial of Telitacicept in Primary Sjögren’s Disease

Vor Bio (Nasdaq: VOR), a clinical-stage biotechnology company transforming the treatment of autoimmune diseases, today announced the dosing of the first patient in UPSTREAM SjD, a global, randomized, double-blind, placebo-controlled Phase 3 trial evaluating telitacicept in adult patients with active primary Sjögren’s disease (SjD), formerly known as Sjögren's syndrome.

“Dosing the first patient in the global Phase 3 UPSTREAM SjD trial represents a significant milestone for telitacicept and for patients living with Sjögren’s disease. As the only BAFF/APRIL inhibitor currently in Phase 3 development for this condition, we believe telitacicept has the potential to address a serious autoimmune disease that currently lacks approved disease-modifying therapies,” said Jean-Paul Kress, M.D., Chief Executive Officer and Chairman of Vor Bio. “In late 2025, RemeGen presented results from a Phase 3 trial conducted in China with telitacicept in the same indication that demonstrated potential best-in-disease activity, with statistically significant and clinically meaningful improvements in both ESSDAI and ESSPRI, the two key, validated EULAR measurements used to assess patient disease burden. These prior results provide important clinical support for dual BAFF/APRIL inhibition as a therapeutic strategy in this disease and give us confidence in telitacicept’s potential to address both systemic disease activity and the symptoms that matter most to patients.”

UPSTREAM SjD will evaluate the efficacy and safety of telitacicept administered subcutaneously with a pre-filled syringe compared to placebo in approximately 250 adult patients with active primary SjD. The primary endpoint is the change from baseline in the EULAR Sjögren’s Syndrome Disease Activity Index (ESSDAI) score at Week 48. The trial is expected to enroll patients who meet the 2016 ACR/EULAR classification criteria for primary SjD and have active disease as defined by an ESSDAI score ≥5. Key secondary endpoints in the UPSTREAM SjD trial will evaluate the effect of telitacicept at Week 48 across systemic disease activity, glandular function, and patient-reported symptoms.

About Sjögren’s Disease

Sjögren’s disease is a chronic autoimmune condition in which overactive B cells drive inflammation, damaging moisture-producing glands and, in many cases, other organs throughout the body. Hallmark symptoms include dry eyes and dry mouth, alongside fatigue, pain, and systemic complications affecting the skin, lungs, kidneys, and nervous system. About one-third of patients develop significant extraglandular involvement, and the disease carries an elevated lymphoma risk, often leading to substantial impairment in daily life.

One of the most common rheumatic autoimmune diseases, Sjögren’s remains underdiagnosed, with roughly half of cases unrecognized and women comprising the vast majority of patients. Despite its prevalence and burden, no approved systemic disease-modifying therapies exist; current care focuses on symptom management with incomplete relief.

About Telitacicept

Telitacicept is a novel, investigational recombinant fusion protein designed to treat autoimmune diseases by selectively inhibiting BLyS (BAFF) and APRIL - two cytokines essential to B cell and plasma cell survival. This dual-target mechanism reduces autoreactive B cells and autoantibody production, key drivers of autoimmune pathology.

Telitacicept is approved in China for systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and generalized myasthenia gravis (gMG). Additional regulatory filings in China are underway, including biologics license applications for primary Sjögren’s disease (SjD) and IgA nephropathy (IgAN).

Vor Bio is advancing global development programs across major autoimmune indications, including a global Phase 3 trial in gMG and SjD to support potential regulatory approvals in the United States, Europe, and Japan.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. The words “aim,” “anticipate,” “can,” “continue,” “could,” “design,” “enable,” “expect,” “initiate,” “intend,” “may,” “on-track,” “ongoing,” “plan,” “potential,” “should,” “target,” “update,” “will,” “would,” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Forward-looking statements in this press release include Vor Bio’s statements regarding telitacicept’s market opportunity, including its potential to address a serious autoimmune disease that currently lacks approved disease-modifying therapies; telitacicept’s potential best-in-disease activity in SjD; telitacicept’s potential to address both systemic activity of SjD and the symptoms that matter most to patients; and other statements that are not historical fact.

Vor Bio may not actually achieve the plans, intentions, or expectations disclosed in these forward-looking statements, and you should not place undue reliance on these forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in these forward-looking statements as a result of various factors, including the data for our product candidates may not be sufficient for obtaining regulatory approval to commercialize products; we may not be able to execute our business plans, including meeting our planned clinical and regulatory milestones and timelines, and possible limitations of financial and other resources. These and other risks are described in greater detail under the caption “Risk Factors” included in Vor Bio’s most recent annual or quarterly report and in other reports it has filed or may file with the Securities and Exchange Commission. The results of the clinical trial described in this press release are based on information reported by RemeGen; Vor Bio has not independently verified this data.

Any forward-looking statements contained in this press release speak only as of the date hereof, and Vor Bio expressly disclaims any obligation to update any forward-looking statements, whether because of new information, future events or otherwise, except as may be required by law.