Xencor Highlights 2022 Corporate Priorities and Portfolio Milestones

Xencor, Inc. (NASDAQ:XNCR), a clinical-stage biopharmaceutical company developing engineered monoclonal antibodies and cytokines for the treatment of cancer and autoimmune diseases, today announced 2022 corporate priorities and anticipated clinical development and research milestones.

“The plug-and-play nature of Xencor’s XmAb^® Fc domains and our protein engineering expertise have enabled a broad portfolio of bispecific antibody and engineered cytokine drug candidates, as well as a multitude of partnerships, which have thus far produced three marketed products,” said Bassil Dahiyat, Ph.D., president and chief executive officer at Xencor. “In 2022, we expect emerging clinical data to continue to support our own mid-stage development plans for vudalimab and plamotamab, and we will continue to initiate new studies with potential to present new data that may define a path to registration for these programs. Additionally, we remain excited by the opportunities to use our technological competitive advantage to address challenging areas of biology and continually grow our portfolio, now with multiple reduced-potency cytokines and CD3 and CD28 T cell engagers in development, both internally at Xencor and with our partners.”

Execute on development plans for mid-stage XmAb^® bispecific antibody programs

Vudalimab (PD-1 x CTLA-4), designed to activate intra-tumoral T cells

Xencor presented updated Phase 1 expansion cohort data in November 2021 and is enrolling a Phase 2 study in patients with metastatic castration-resistant prostate cancer (mCRPC), where vudalimab is being evaluated as a monotherapy or in combination depending on the tumor’s molecular subtype. Xencor plans to:

• Initiate a second Phase 2 study, evaluating vudalimab in patients with advanced pelvic tumors, including clinically defined high-risk mCRPC and certain gynecologic malignancies.
• Present initial data from the Phase 2 study in mCRPC, in the second half of 2022.

Plamotamab (CD20 x CD3), for B-cell malignancies

Xencor presented updated Phase 1 dose-escalation data in December 2021 and is currently recruiting non-Hodgkin lymphoma patients in expansion cohorts of plamotamab monotherapy at the Phase 2 recommended dose. Xencor entered a global collaboration and license agreement with Janssen Biotech, Inc., one of the Janssen Pharmaceutical Companies of Johnson & Johnson, to expand the Company’s strategy to develop plamotamab as part of multiple highly active chemotherapy-free regimens across B-cell cancers. Xencor plans to:

• Initiate potentially registration-enabling Phase 2 study, evaluating plamotamab in combination with tafasitamab and lenalidomide, in patients with relapsed or refractory DLBCL.
• Incorporate subcutaneous administration into the ongoing Phase 1 monotherapy study.
• Present data from Phase 1 expansion cohorts, in the second half of 2022.
• Develop B-cell targeted CD28 bispecific antibodies to selectively enhance T-cell cytotoxic activity in combination with plamotamab.

Advance multiple potency-reduced XmAb^® cytokine programs in oncology and autoimmune disease

Xencor’s engineered, potency-reduced cytokines are designed to expand select immune cell populations, to have longer circulating half-life and to be tolerable, active and easy to administer. XmAb cytokines incorporate Xtend™ extended half-life technology.

XmAb306, potency-reduced IL15/IL15Rα-Fc fusion protein

Recently, Xencor announced encouraging initial dose-escalation data from an ongoing Phase 1 study in patients with advanced solid tumors, in which the preliminary safety profile, biological activity and signs of anti-tumor activity provide initial validation for the Company’s approach to engineering cytokine therapeutics. Xencor plans to:

• Announce new clinical studies of XmAb306 in combination with other agents, such as NK- or T-cell recruiting therapies in collaboration with the Company’s co-development partner.

XmAb564, potency-reduced IL2-Fc fusion targeting regulatory T cells in autoimmune disease

Xencor plans to:

• Present tolerability, durability and biomarker data from the ongoing Phase 1 single-ascending dose study in healthy volunteers.
• Identify development indications and initiate a multiple-ascending dose study in select patient populations.

XmAb662, potency-reduced IL12-Fc fusion protein designed to increase tumor immunogenicity

Xencor plans to:

• Submit an investigational new drug (IND) application in 2022, and initiate a Phase 1 study in patients with advanced solid tumors in 2023.

Xencor plans to present preclinical data from additional cytokine-Fc programs in 2022.

Expand the Company’s portfolio with the first internally developed XmAb^® 2+1 CD3 and XmAb^® CD28 bispecific antibodies advancing into Phase 1 clinical studies

XmAb819 (ENPP3 x CD3), XmAb 2+1 bispecific antibody for renal cell carcinoma (RCC)

The multivalent XmAb 2+1 bispecific antibody format enables greater selectivity for tumor cells compared to normal cells, which also express ENPP3 at lower levels. Xencor plans to:

• Initiate a Phase 1 study evaluating XmAb819 in patients with RCC in the first half of 2022.

XmAb808 (B7-H3 x CD28), tumor-selective, co-stimulatory CD28 bispecific antibody

CD28 is a key immune co-stimulatory receptor on T cells; however, the ligands that activate T cells through CD28 are usually not expressed on tumor cells. Targeted CD28 bispecific antibodies may provide conditional co-stimulation of T cells, for example, to T cells recognizing neoantigens or in concert with CD3 T-cell engaging bispecific antibodies. XmAb808 targets the broadly expressed tumor antigen B7-H3. Xencor plans to:

• Submit an IND application in the first half of 2022, and initiate a Phase 1 study in patients with advanced solid tumors in the second half of 2022.

Cash Position and Financial Guidance

Xencor ended the fourth quarter of 2021 with unaudited cash, cash equivalents, receivables and marketable debt securities totaling approximately $660 million. Based on current operating plans, Xencor expects to have sufficient cash resources to fund research and development programs and operations through 2025.

About Xencor, Inc.

Xencor is a clinical-stage biopharmaceutical company developing engineered monoclonal antibodies and cytokines for the treatment of cancer and autoimmune diseases. Currently, 22 candidates engineered with Xencor's XmAb^® technology are in clinical development internally and with partners. Xencor's XmAb antibody engineering technology enables small changes to the structure of proteins resulting in new mechanisms of therapeutic action. For more information, please visit www.xencor.com.

Forward Looking Statements

Certain statements contained in this press release may constitute forward-looking statements within the meaning of applicable securities laws. Forward-looking statements include statements that are not purely statements of historical fact, and can generally be identified by the use of words such as “potential,” “can,” “will,” “plan,” “may,” “could,” “would,” “expect,” “anticipate,” “seek,” “look forward,” “believe,” “committed,” “investigational,” and similar terms, or by express or implied discussions relating to Xencor’s business, including, but not limited to, statements regarding planned additional clinical trials, the quotations from Xencor's president and chief executive officer and other statements that are not purely statements of historical fact. Such statements are made on the basis of the current beliefs, expectations, and assumptions of the management of Xencor and are subject to significant known and unknown risks, uncertainties and other factors that may cause actual results, performance or achievements and the timing of events to be materially different from those implied by such statements, and therefore these statements should not be read as guarantees of future performance or results. Such risks include, without limitation, the risks associated with the process of discovering, developing, manufacturing and commercializing drugs that are safe and effective for use as human therapeutics and other risks, including the ability of publicly disclosed preliminary clinical trial data to support continued clinical development and regulatory approval for specific treatments, in each case as described in Xencor's public securities filings. For a discussion of these and other factors, please refer to Xencor's annual report on Form 10-K for the year ended December 31, 2020 as well as Xencor's subsequent filings with the Securities and Exchange Commission. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. This caution is made under the safe harbor provisions of the Private Securities Litigation Reform Act of 1995, as amended to date. All forward-looking statements are qualified in their entirety by this cautionary statement and Xencor undertakes no obligation to revise or update this press release to reflect events or circumstances after the date hereof, except as required by law.

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