XNCR

EX-99.1

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PRESENTATION DATED OCTOBER 26, 2026

Exhibit 99.1

® Designing Proteins Delivering Medicines Updated Results from Dose Expansion Cohorts in the Phase 1 Study of XmAb819 October 26, 2026

2 Today's Speakers Bassil Dahiyat, Ph.D. President & Chief Executive Officer Xencor Management Guest Speaker Sumanta Pal, M.D., F.A.S.C.O. Professor, Department of Medical Oncology & Therapeutics Research Vice Chair of Academic Affairs Co-director, Kidney Cancer Program City of Hope Comprehensive Cancer Center Dane Leone Executive Vice President & Chief Strategy Officer John Desjarlais, Ph.D. Executive Vice President & Chief Scientific Officer Jeff Chou Senior Vice President, Head of Oncology Clinical Development

3 Today's Agenda XmAb819 development strategy Updated Phase 1 results of XmAb819, a novel ENPP3 x CD3 bispecific, in advanced clear cell renal cell carcinoma (ccRCC) Overview & XmAb® 2+1 T-cell Engagers Summary and Q&A Additional results

4 Forward-Looking Statements Certain statements contained in this presentation, other than statements of historical fact, may constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Such statements include, but are not limited to, statements regarding Xencor's development plans and timelines; potential regulatory actions; expected use of cash resources; the timing and results of clinical trials; the plans and objectives of management for future operations; and the potential markets for Xencor's product and development candidates. Forward-looking statements are based on the current expectations of management and upon what management believes to be reasonable assumptions based on information currently available to it, and involve numerous risks and uncertainties, many of which are beyond Xencor's control. These risks and uncertainties could cause future results, performance or achievements to differ significantly from the results, performance or achievements expressed or implied by such forward-looking statements. Such risks include, but are not limited to, potential delays in development timelines or negative preclinical or clinical trial results, reliance on third parties for development efforts and changes in the competitive landscape including changes in the standard of care for treatment of diseases for which we are developing product candidates, as well as other risks described in Xencor's filings with the Securities and Exchange Commission, including Xencor's most recent Annual Report on Form 10-K and subsequently filed Quarterly Reports on Form 10-Q. Xencor expressly disclaims any duty, obligation or undertaking to update or revise any forward-looking statements contained herein to reflect any change in Xencor's expectations with regard thereto or any subsequent change in events, conditions or circumstances on which any such statements are based, except in accordance with applicable securities laws. For all forward-looking statements, we claim the protection of the safe harbor for forward looking statements contained in the Private Securities Litigation Reform Act of 1995. Disclaimer: We use our trademarks and our logo in this presentation. This presentation also includes trademarks, tradenames and service marks that are the property of other organizations. Solely for convenience, trademarks and tradenames referred to in this presentation appear without the "®" and "TM" symbols, but those references are not intended to indicate, in any way, that we will not assert, to the fullest extent under applicable law, our rights or that the applicable owner will not assert its rights, to these trademarks and tradenames.

5 Xencor is at the forefront of bispecific T-cell engagers in solid tumors with the 3rd late-stage XmAb® program expected in 2027 XmAb819 ENPP3 x CD3 Planned, potential registration-enabling study start in 2027 Advanced ccRCC and ENPP3+ tumors 100% Wholly Owned Xaluritamig STEAP1 x CD3 Phase 3 Prostate cancer, Ewing sarcoma Mid- to high-single digit royalty and up to $225 million in milestone payments1 ASP2138 CLDN18.2 x CD3 Phase 3 Gastric/GEJ cancer, Pancreatic cancer High single- to low double-digit royalty and up to $232.5 million in milestone payments1 XmAb® Fc Domains Augment native immune functions in molecules and/or control their structure, while preserving desired attributes (e.g., Xtend extended half-life or heterodimeric Fc domain for bispecific antibodies). XmAb® toolkits enable rapid prototyping and lead optimization XmAb® 2+1 Formats Designed to enable antibodies to bind more avidly and selectively kill cells with higher antigen density, potentially sparing normal cells XmAb® 2+1 programs in solid tumor oncology advancing internally and with leading pharmaceutical partners 1 Remaining as of June 30, 2026 ccRCC clear cell renal cell carcinoma GEJ gastro-esophageal junction

6 Oncology Clinical Studies Our focus on

EX-99.1

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EX-99.1

Document

Exhibit 99.1

Xencor Reports Second Quarter 2026 Financial Results

-- XmAb819 ccRCC expansion cohorts to be presented in an oral session at ESMO 2026; multiple Phase 1 sub-studies in earlier lines of therapy and additional indications now open for enrollment or planned --

-- XmAb942 enrollment in XENITH-UC remains on track with primary endpoint of the 12-week induction period expected in 2H27 --

-- XmAb412 (TL1A x IL23p19) first-in-human healthy participant study open for enrollment --

PASADENA, Calif.--August 5, 2026-- Xencor, Inc. (NASDAQ:XNCR), a clinical-stage biopharmaceutical company developing engineered antibodies for the treatment of cancer and autoimmune diseases, today reported financial results for the second quarter ended June 30, 2026.

“We are excited to present XmAb819 results at ESMO this fall and for other fast-approaching key milestones across our wholly owned clinical pipeline,” said Bassil Dahiyat, Ph.D., president and chief executive officer at Xencor. “Enrollment remains on track for updates later this year for XmAb942 in the XENITH-UC study and for our two B-cell depleting bispecifics, plamotamab and XmAb657, in their respective Phase 1 studies. And we recently started the Phase 1 study of XmAb412, our first XenLock™ bispecific antibody, and plan to have healthy participant data in the first half of 2027. Xencor’s focus on clinical execution and data delivery is setting us up for an accelerating tempo of anticipated readouts in 2027 and beyond.”

“Consistent with our focus on efficient clinical decision-making, we have prioritized the ongoing combination study of XmAb541 and XmAb808, which provides tumor-targeted co-stimulation through CD28 agonism, after observing moderate anti-tumor activity from early monotherapy data of XmAb541. CLDN6 remains a challenging tumor target, and we hope to expand upon an emerging therapeutic window through the orthogonal targeting provided by XmAb808.”

Wholly Owned Pipeline Overview

XmAb819 (ENPP3 x CD3), a potential first-in-class, tumor-targeted, T-cell engaging XmAb® 2+1 bispecific antibody in development for patients with clear cell renal cell carcinoma and other tumors with high ENPP3 expression, including colorectal cancer, non-small cell lung cancer and papillary renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC): On track to initiate a registration enabling study of XmAb819 as a monotherapy in advanced ccRCC during 2027.

•Phase 1 results for patients with advanced ccRCC were accepted for a proffered paper oral presentation at the European Society For Medical Oncology (ESMO) Congress 2026, to be held October 23-27 in Madrid, Spain. The presentation during ESMO will focus on dose levels in intravenous expansion cohorts under evaluation as recommended Phase 3 doses (RP3D).

•Dose escalation of subcutaneous administration in advanced ccRCC is ongoing with evaluation for further development expected prior to a registration enabling study.

•A sub-study for patients with intermediate- or poor-risk advanced ccRCC who have progressed after nivolumab in combination with ipilimumab as a first-line treatment (IO doublet therapy) is planned to open for enrollment in the third quarter of 2026.

•A sub-study evaluating the combination of XmAb819 and anti-PD1 therapy in patients with advanced ccRCC is currently being planned.

Additional tumors with high ENPP3 expression

•A sub-study for patients with ENPP3+ advanced colorectal cancer, non-small cell lung cancer and papillary renal cell carcinoma began enrollment in the second quarter of 2026.

XmAb541 (CLDN6 x CD3) in combination with XmAb808 (B7-H3 x CD28), in Phase 1 clinical development for T-cell engagement of Claudin-6 expressing tumors, including high-grade serous ovarian cancer

XmAb541 development in the ongoing Phase 1 dose-escalation study in combination with XmAb808 has been prioritized. XmAb541 monotherapy expansion cohorts at the putative RP3D (60 mg dosed every 3 weeks) in high-grade serous ovarian carcinoma (TPS≥50) and germ cell tumors are expected to complete enrollment by year end, with the data supporting combination development with XmAb808. The Phase 1 dose-escalation study of XmAb541 and XmAb808 is ongoing and expected to reach the combination’s target dose range in 2027. Prioritization of the combination is anticipated to reduce projected overall XmAb541 program expense for 2027 and 2028.

XmAb541 Clinical Data

•Emerging data from XmAb541 monotherapy indicate clinical activity to date at the putative RP3D in heavily-pretreated patients, with an approximate 14% overall response rate (ORR) in patients with ovarian cancer and an approximate 28% ORR in patients with germ cell tumors, which supports further evaluation in combination with XmAb808 to provide tumor-targeted CD28 agonism and additional T-cell stimulation.

•Potential additional anti-tumor activity was observed at doses above 60 mg, but reversible hearing

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