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Exhibit 99.1 xencor Xencor Reports First Quarter 2021 Financial Results -- Management to Host Conference Call at 4:30 p.m. ET Today -- MONROVIA , Calif .-- May 5 , 2021-- Xencor , Inc. ( NASDAQ : XNCR ) , a clinical - stage biopharmaceutical company developing engineered monoclonal antibodies and cytokines for the treatment of cancer and autoimmune diseases , today reported financial results for the first quarter ended March 31 , 2021 and provided a review of recent business and clinical highlights . " We continue to expand and mature our clinical portfolio of XmAbⓇ drug candidates , recently initiating a Phase 1 study for our second cytokine program , XmAb564 , a wholly owned IL - 2 - Fc fusion protein , in healthy volunteers . We engineered this molecule to preferentially activate regulatory T cells , an emerging mechanism for treating patients with autoimmune diseases , " said Bassil Dahiyat , Ph.D. , president and chief executive officer at Xencor . " Additionally , at the AACR meeting , we presented preclinical data from multiple early - stage programs that highlight our protein engineering expertise with our third cytokine , a wholly owned IL - 12 - Fc fusion protein , as well as the potential of our CD28 platform and XmAb 2 + 1 bispecific antibody format . Looking ahead , we will continue to present maturing data from our clinical - stage programs , and we have plans to initiate several additional clinical studies this year and early 2022 , including a Phase 2 study in prostate cancer with XmAb717 , our PD - 1 x CTLA - 4 bispecific antibody . " Recent Business and Portfolio Highlights • XmAb564 ( IL - 2 - Fc Cytokine ) : XmAb564 is a wholly owned , monovalent IL - 2 - Fc fusion protein , engineered to selectively activate and expand regulatory T cells ( Tregs ) for the potential treatment of patients with autoimmune diseases . XmAb564 is engineered with reduced binding affinity for IL- 2's beta receptor and increased binding affinity for its alpha receptor . In preclinical studies , XmAb564 was well - tolerated , promoted the selective and sustained expansion of Tregs and exhibited a favorable pharmacokinetic profile . In April 2021 , the first subject was dosed in a randomized , double - blind , placebo - controlled Phase 1 clinical study evaluating the safety and tolerability of XmAb564 , administered subcutaneously in healthy adult volunteers . Preclinical Presentations at AACR : At the 2021 AACR Annual Meeting , the Company presented four posters highlighting several preclinical - stage programs , including its IL - 12 - Fc cytokine program , two XmAb 2 + 1 bispecific antibodies ( Claudin - 6 x CD3 and GPC3 x CD3 ) , and a PD - L1 x CD28 bispecific program . Such targeted CD28 bispecific antibodies , a new class of T cell engager , 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 . The Company is also advancing through preclinical development a wholly owned lead CD28 candidate , a B7 - H3 x CD28 bispecific antibody , which will be evaluated for the treatment of patients with a range of solid tumors . New Academic Collaboration with UCLA : In February , the Company entered an agreement with UCLA to develop novel therapeutic antibodies , pairing novel targets proposed by scientists at UCLA and Xencor's modular suite of XmAb technology platforms . The UCLA Technology Development Group will work with faculty to propose potential antibody drug candidates . For selected candidates , the Company and UCLA expect to use a framework with predefined terms to enter sponsored research agreements and potential license agreements .