Atreca (BCEL) Announces Expansion of Preclinical Pipeline

Atreca, Inc. (Atreca) (NASDAQ: BCEL), a clinical-stage biotechnology company focused on developing novel therapeutics generated through a unique discovery platform based on interrogation of the active human immune response, today announced a licensing agreement with Zymeworks Inc. (Zymeworks) (NYSE: ZYME) to utilize their ZymeLink™ technology to develop novel antibody-drug conjugates (ADCs) and declared ATRC-301, an ADC targeting a novel epitope on EphA2, as the Company’s next clinical candidate. Atreca management will discuss the agreement, ATRC-301, and its earlier stage pipeline programs during today’s R&D Day beginning at 4:15pm EDT.

"We are pleased to be hosting our first R&D Day and providing an update on our preclinical pipeline in oncology,” said John Orwin, Chief Executive Officer of Atreca. “We are particularly excited to announce our next clinical candidate, ATRC-301, an ADC of an Atreca-discovered antibody targeting EphA2 conjugated using Zymeworks’ proprietary ZymeLink™ platform. Our new agreement with Zymeworks enables us to develop up to three potential ADC products using their technology. Taken together, today’s announcements demonstrate the productivity of our discovery platform and research organization, as well as the potential value of our preclinical programs. Given this productivity and the resulting expansion of our pipeline of oncology programs, we are targeting one additional Investigational New Drug (IND) application per year beginning with ATRC-301 in the second half of 2023.”

Zymeworks Agreement

As part of the licensing agreement with Zymeworks, Atreca’s novel antibodies will be conjugated using ZymeLink™, Zymeworks’ suite of proprietary cytotoxins, linkers, and conjugation technologies. The agreement includes a two-year research term for Atreca to evaluate antibodies as ADC’s using ZymeLink™ with the option for a third year, during which Atreca can acquire up to three commercial licenses to develop three unique ADC programs. Work between the two companies has been ongoing since late 2020.

ZymeLink™ is a next-generation drug conjugate platform that provides a suite of proprietary auristatin-based or hemiasterlin-based cytotoxins, complete with stable, cleavable linkers. Antibodies conjugated using the ZymeLink™ platform have IgG1-like PK & exposure, have demonstrated tolerability and support a wide therapeutic window.

“Zymeworks has developed a leading next-generation ADC technology, and we are pleased to announce a licensing agreement to utilize their ZymeLink™ platform for our initial ADC programs,” said Tito A. Serafini, Ph.D., Chief Strategy Officer of Atreca. “A substantial fraction of the tumor-binding antibodies that we discover from patients are active in ADC assays, and we view this as a potentially high-value area for further investment and development.”

ATRC-301

ATRC-301, Atreca’s next clinical candidate, is an ADC that selectively targets a novel, membrane-proximal epitope on erythropoietin-producing hepatocellular receptor A2 (EphA2). EphA2 is a validated and potentially high value target that is widely expressed across several types of cancer, with 12 tumor types displaying prevalence of the target epitope of 50% or greater in human tumor samples evaluated. ATRC-301 has demonstrated potent, dose-dependent in vivo tumor regression in mice with no significant toxicity signals yet observed in rats after single doses of up to and including 30mg/kg. Atreca has initiated IND-enabling studies, including a non-human primate toxicology study for which data are expected in 2H22, and anticipates submitting an IND application for ATRC-301 in 2H23. Atreca also has lead stage CD3-engager targeting EphA2 in development.

Other Preclinical Programs

Atreca is advancing multiple additional lead-stage programs in oncology, including ADC leads APN-497444 and APN–959038, CD3-engager lead APN-346958, and IL-15 superagonist (SA) conjugate lead APN-541885. Each program is based on an antibody identified via Atreca’s discovery platform from an active human immune response antibody, and upon further evaluation displayed strong and tumor-selective immunoreactivity against targets present on multiple tumor types across groups of patient samples. In their weaponized formats, each lead has demonstrated anti-tumor activity in in vivo preclinical studies. The targets bound by the antibodies vary in class and include both novel epitopes of known cancer targets as well as entirely novel target antigens in oncology.

R&D Day Webcast and Conference Call Details

The live R&D Day webcast, including accompanying slides, can be accessed through the Events & Presentations section of the Company's website at https://ir.atreca.com/news-and-events/event-calendar. To access the event by telephone, please dial (800) 373-6606 (United States) or (409) 937-8918 (international) and reference the conference ID 3490903. An archived replay of the webcast will be available on the Company's website following the live event.

About Atreca, Inc.

Atreca is a clinical-stage biopharmaceutical company developing novel antibody-based immunotherapeutics generated by its differentiated discovery platform. Atreca's platform allows access to an unexplored landscape in oncology through the identification of unique antibody-target pairs generated by the human immune system during an active immune response against tumors. These antibodies provide the basis for first-in-class therapeutic candidates, such as our lead product candidate ATRC-101. A Phase 1b study evaluating ATRC-101 in multiple solid tumor cancers is currently enrolling patients. For more information on Atreca, please visit www.atreca.com.

About Zymeworks Inc.

Zymeworks is a clinical-stage biopharmaceutical company dedicated to the discovery, development and commercialization of next-generation multifunctional biotherapeutics. Zymeworks’ suite of therapeutic platforms and its fully integrated drug development engine enable precise engineering of highly differentiated product candidates. Zymeworks’ lead clinical candidate, zanidatamab, is a novel Azymetric™ HER2-targeted bispecific antibody currently being evaluated in multiple Phase 1, Phase 2, and pivotal clinical trials globally as a targeted treatment option for patients with solid tumors that express HER2. Zymeworks’ second clinical candidate, ZW49, is a novel bispecific HER2‑targeted antibody-drug conjugate currently in Phase 1 clinical development and combines the unique design and antibody framework of zanidatamab with Zymeworks’ proprietary ZymeLink™ linker and cytotoxin. Zymeworks is also advancing a deep preclinical pipeline in oncology (including immuno-oncology agents) and other therapeutic areas. In addition, its therapeutic platforms are being leveraged through strategic partnerships with global biopharmaceutical companies. For more information on our ongoing clinical trials visit www.zymeworksclinicaltrials.com. For additional information about Zymeworks, visit www.zymeworks.com and follow @ZymeworksInc on Twitter.

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