Equillium Announces Positive Interim Results from the EQUALISE Study in Subjects with Lupus Nephritis

Itolizumab demonstrates clinically meaningful response in highly proteinuric subjects:

5 of 6 (83%) subjects achieved complete or partial response and 4 of 6 (67%) subjects achieved > 80% reduction in urine protein creatinine ratio (UPCR) by week 28

8 of 12 (67%) subjects achieved > 50% reduction in UPCR (6 subjects still dosing)

Itolizumab continues to demonstrate favorable safety and tolerability through six months of treatment

Management will host a conference call and webcast today at 8:00 am ET

Equillium, Inc. (NASDAQ:EQ), a clinical-stage biotechnology company focused on developing novel therapeutics to treat severe autoimmune and inflammatory disorders with high unmet medical need, today announced interim results from the Type B portion of the EQUALISE study evaluating itolizumab, a first-in-class anti-CD6 monoclonal antibody selectively targeting the CD6-ALCAM pathway, in patients with lupus nephritis (LN).

"Despite recently approved therapies, 60% of lupus nephritis patients are failing to achieve a complete response at 12 months, highlighting the need for new medicines with differentiated mechanisms," said Bruce Steel, chief executive officer at Equillium. "We are very encouraged by the interim data from the LN portion of the EQUALISE study as we observed compelling responses in a patient population with significantly greater baseline proteinuria than recent studies, with a mean baseline UPCR of 5.8 grams. At end of study, 83% of patients achieved a complete or partial clinical response, with 67% reaching a greater than 80% reduction in UPCR. The interim data adds to our conviction in the clinical activity of itolizumab and the potential to be an impactful therapy for patients with lupus nephritis. We look forward to continuing to enroll patients in the Type B portion of the EQUALISE study and anticipate sharing topline data in mid-2023. In parallel, we are engaged with key opinion leaders to prepare for later stage development that we expect can support potential product registration."

"I'm impressed with these promising early and deep reductions in proteinuria, especially given the high nephrotic baseline levels," said Dr. Kenneth Kalunian, professor of clinical medicine at the University of California San Diego School of Medicine and the lead principal investigator on the EQUALISE trial. "What is particularly striking are the higher overall response rates observed early in the treatment course that are not typically achieved with standard of care alone and that look competitive with data emerging from the recently approved drugs. As a clinician, an ideal therapy would safely and rapidly reduce the levels of proteinuria in a greater number of patients as this has been shown to be associated with improved long-term outcomes. These interim results from the EQUALISE study are encouraging and provide the type of signal we're looking for to advance a drug to larger controlled trials."

The Type B portion of the EQUALISE study in patients with active proliferative LN is evaluating the safety, tolerability and clinical activity of subcutaneous delivery of itolizumab. Patients must present with greater than 1 gram of proteinuria and positive biopsy to be eligible for the study. During the 24-week treatment period, patients receive a subcutaneous dose of 1.6 mg/kg every two weeks, with follow up out to 36 weeks. Consistent with standard of care, patients on study also receive 2-3 g/day of mycophenolate mofetil/mycophenolic acid (MMF/MPA), and patients may receive pulse systemic corticosteroids that are rapidly tapered.

For this interim analysis, 13 subjects have been enrolled and dosed, with 11 subjects reaching at least 12 weeks of treatment and 6 subjects reaching 28 weeks or the end of study (EOS). Based on published guidelines for the management of lupus nephritis from the European League Against Rheumatism (EULAR) and European Renal Association-European Dialysis and Transplant Association (ERA-EDTA), clinical activity assessments in this study are focused on the change in UPCR from baseline; proportion of apLN subjects with a complete response (CR), defined as 50% or greater reduction in UPCR and less than 0.5-0.7 g/g; and proportion of subjects achieving a partial response (PR), defined as 50% or greater reduction in UPCR.

Key findings from the interim analysis of the Type B portion of the EQUALISE study in lupus nephritis:

• Subjects were highly proteinuric: baseline mean UPCR of 5.8 g/g
• Clinically meaningful responses were observed:
  • By week 28 (or EOS):
    • 3 of 6 (50%) subjects achieved CR (UPCR < 0.7 g/g)
    • 2 of 6 (33%) subjects achieved PR (UPCR > 50% reduction)
    • 4 of 6 (67%) subjects achieved greater than 80% reduction in UPCR
  • In all subjects receiving more than one dose:
    • 8 of 12 (67%) subjects achieved greater than 50% reduction in UPCR
    • Average reduction of 60% in UPCR (over 3g of proteinuria)
    • Subjects titrated steroid dose to < 7.5 mg/day consistent with EULAR/ERA-EDTA recommendations
• Itolizumab was generally safe and well tolerated with no drug related serious adverse events or treatment discontinuations

Data reported from the Type B portion of the EQUALISE study are preliminary and subject to change as more patient data become available.

Top-line data from the Type B portion of the EQUALISE study in patients with lupus nephritis is expected to be announced mid-2023.

Webcast and Conference Call

Management will host a conference call accompanied by a slide presentation to discuss the interim data from the Type B portion of the EQUALISE study in patients with lupus nephritis, for analysts and institutional investors, at 8:00 am ET today, September 27, 2022. To access the call, please dial (888) 350-3846 or (646) 960-0251 and, if needed, provide confirmation number 8770084. A live webcast of the call will also be available on the company's Investor Relations page at https://www.equilliumbio.com/investors/events-and-presentations/default.aspx. The webcast will be archived for 180 days.

About Systemic Lupus Erythematosus (SLE) & Lupus Nephritis (LN)

SLE is an autoimmune disease in which the immune system attacks its own tissues, causing widespread inflammation and tissue damage in the affected organs. It can affect the joints, skin, brain, lungs, kidneys, and blood vessels. LN is a serious complication of SLE, occurring in approximately 30% – 60% of individuals with SLE. LN involves the body's own immune system attacking the kidneys, causing inflammation and significantly reducing kidney function over time. LN is associated with an increase in mortality compared with the general population and may lead to end-stage renal disease.

About the EQUALISE Study

The EQUALISE study is a two-part Phase 1b open-label proof-of-concept study of itolizumab in patients with SLE and LN. The Type A portion of the study was a multiple ascending-dose clinical study evaluating the safety and tolerability of subcutaneous delivery of itolizumab over a two-week treatment period in 35 patients with SLE. The Type B portion of the study, currently enrolling, is evaluating the safety, tolerability and clinical activity of subcutaneous delivery of itolizumab dosed at 1.6 mg/kg every two weeks over a 24-week treatment period in up to 20 patients with active proliferative LN.

About Itolizumab

Itolizumab is a clinical-stage, first-in-class anti-CD6 monoclonal antibody that selectively targets the CD6-ALCAM pathway. This pathway plays a central role in modulating the activity and trafficking of T cells that drive a number of immuno-inflammatory diseases. Equillium acquired rights to itolizumab through an exclusive partnership with Biocon Limited.

About Equillium

Equillium is a clinical-stage biotechnology company leveraging a deep understanding of immunobiology to develop novel therapeutics to treat severe autoimmune and inflammatory disorders with high unmet medical need. The company's pipeline consists of the following novel immunomodulatory assets targeting immuno-inflammatory pathways. Itolizumab, a first-in-class monoclonal antibody that targets the CD6-ALCAM signaling pathway which plays a central role in the modulation of effector T cells, is currently in a Phase 3 study for patients with acute graft-versus-host disease (aGVHD) and is in a Phase 1b study for patients with lupus/lupus nephritis. EQ101, a first-in-class tri-specific cytokine inhibitor that selectively targets IL-2, IL-9, and IL-15, is Phase 2 ready and expected to begin enrolling patients in an alopecia areata study in the fourth quarter of 2022. EQ102, a bi-specific cytokine inhibitor that selectively targets IL-15 and IL-21, is ready for clinical development and expected to begin enrolling patients in a Phase 1 study anticipated to include normal healthy volunteers and celiac disease patients, in the fourth quarter of 2022.

For more information, visit www.equilliumbio.com.

Forward Looking Statements

Statements contained in this press release regarding matters that are not historical facts are "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements may be identified by the use of words such as "anticipate", "believe", "could", "continue", "expect", "estimate", "may", "plan", "outlook", "future" and "project" and other similar expressions that predict or indicate future events or trends or that are not statements of historical matters. Because such statements are subject to risks and uncertainties, many of which are outside of the Company's control, actual results may differ materially from those expressed or implied by such forward-looking statements. Such statements include, but are not limited to statements regarding the potential benefit of treating patients with aGVHD or lupus/lupus nephritis with itolizumab, Equillium's plans and expected timing for developing itolizumab including the expected timing of initiating, completing and announcing further results from the EQUALISE study, Equillium's plans and expected timing for developing EQ101 and EQ102 including the expected timing of initiating, completing and announcing further results from Phase 2 and Phase 1 studies, respectively, the potential for any of Equillium's ongoing or planned clinical studies to show safety or efficacy, and Equillium's plans and expected timing for developing its product candidates and potential benefits of its product candidates. Risks that contribute to the uncertain nature of the forward-looking statements include: uncertainties related to the abilities of the leadership team to perform as expected; Equillium's ability to execute its plans and strategies; risks related to performing clinical studies; the risk that interim results of a clinical study do not necessarily predict final results and that one or more of the clinical outcomes may materially change as patient enrollment continues, following more comprehensive reviews of the data, and as more patient data become available; potential delays in the commencement, enrollment and completion of clinical studies and the reporting of data therefrom; the risk that studies will not be completed as planned; Equillium's plans and product development, including the initiation and completion of clinical studies and the reporting of data therefrom; whether the results from clinical studies will validate and support the safety and efficacy of Equillium's product candidates; changes in the competitive landscape; uncertainties related to Equillium's capital requirements; and having to use cash in ways or on timing other than expected and the impact of market volatility on cash reserves. These and other risks and uncertainties are described more fully under the caption "Risk Factors" and elsewhere in Equillium's filings and reports, which may be accessed for free by visiting EDGAR on the SEC web site at http://www.sec.gov and on the Company's website under the heading "Investors." Investors should take such risks into account and should not rely on forward-looking statements when making investment decisions. All forward-looking statements contained in this press release speak only as of the date on which they were made. Equillium undertakes no obligation to update such statements to reflect events that occur or circumstances that exist after the date on which they were made.

Where You Can Find Additional Information

This communication does not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval with respect to the proposed merger pursuant to which Equillium will acquire Metacrine, Inc. (Metacrine) or otherwise. No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended. In connection with Equillium's pending acquisition of Metacrine, we will file a registration statement on Form S-4 containing a joint proxy statement/prospectus of Equillium and Metacrine and other documents concerning the proposed Merger with the Securities and Exchange Commission (the "SEC"). WE URGE INVESTORS TO READ THE JOINT PROXY STATEMENT/PROSPECTUS AND THESE OTHER MATERIALS CAREFULLY WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT US, METACRINE AND THE PROPOSED MERGER. Investors may obtain free copies of the joint proxy statement/prospectus (when available) and other documents filed by us and Metacrine with the SEC at the SEC's website at www.sec.gov. Free copies of the joint proxy statement/prospectus (when available) and our other SEC filings are also available on our website at http://www.equilliumbio.com/. Equillium, Metacrine and their respective directors, executive officers, certain members of management and certain employees may be deemed, under SEC rules, to be participants in the solicitation of proxies with respect to the proposed merger. Information regarding our officers and directors is included in our Definitive Proxy Statement on Schedule 14A filed with the SEC on April 13, 2022 with respect to its 2022 Annual Meeting of Stockholders. Information regarding Metacrine's officers and directors is included in Metacrine's Definitive Proxy Statement on Schedule 14A filed with the SEC on April 7, 2022 with respect to its 2022 Annual Meeting of Stockholders. This document is available free of charge at the SEC's website at www.sec.gov or by going to Metacrine's Investors page on its corporate website at www.metacrine.com. This document is available free of charge at the SEC's website at www.sec.gov or by going to our Investors page on its corporate website at www.equilliumbio.com. Additional information regarding the persons who may, under the rules of the SEC, be deemed participants in the solicitation of proxies in connection with the proposed Merger, and a description of their direct and indirect interests in the proposed Merger, which may differ from the interests of our or Metacrine's stockholders generally, will be set forth in the joint proxy statement/prospectus when it is filed with the SEC.

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