On May 7, 2026 ALX Oncology Holdings Inc. ("ALX Oncology" Nasdaq: ALXO), a clinical-stage biotechnology company advancing a pipeline of novel therapies designed to treat cancer and extend patients’ lives, reported that data from exploratory analyses in the Phase 1b/2 clinical trial evaluating the company’s investigational CD47-inhibitor evorpacept in combination with Jazz Pharmaceuticals’ zanidatamab (ZIIHERA) in patients with heavily pre-treated HER2-positive metastatic breast cancer (mBC) were presented for the first time today in a poster session at the ESMO (Free ESMO Whitepaper) Breast Cancer 2026 congress. The findings show that patients with centrally confirmed HER2-positive (ccHER2-positive) mBC and high CD47 expression experienced a promising, durable response.

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Specifically, patients in the trial with ccHER2-positive disease and high CD47 expression (defined as total membrane staining of >20%) had a confirmed objective response rate (cORR) of 100% (n=5/5), while the cORR was 25% (n=1/4) among those with lower CD47 expression (<20%). Those patients whose tumors expressed higher levels of CD47 also had longer median progression-free survival (mPFS): 22.1 months as compared to 3.4 months in the low-CD47 expression group. The median duration of response (mDOR) among patients whose tumors expressed high levels of CD47 was also notable at 20.2 months.

"There is a large and growing population of patients with advanced breast cancer who need novel treatment options once their disease has progressed following treatment with currently available therapies, including trastuzumab deruxtecan," said Funda Meric-Bernstam, M.D., Chair of the Department of Investigational Cancer Therapeutics at The University of Texas MD Anderson Cancer Center, who presented the findings today. "Our data suggest that adding evorpacept to HER2-targeted agents may provide one such option, and we may be able to optimize patient selection for these regimens by using a biomarker-driven approach that incorporates CD47."

The Phase 1b/2 open-label, multi-center clinical trial (NCT05027139) evaluating evorpacept plus zanidatamab included patients with heavily pre-treated HER2-positive mBC (median of five prior HER2-targeted therapies), all of whom had received prior ENHERTU therapy. The primary trial results, presented at the 2024 San Antonio Breast Cancer Symposium (SABCS), demonstrated that the investigational combination generated promising anti-tumor activity and a manageable safety profile.

The exploratory analyses comprised 24 patients, including 10 with ccHER2-positive disease. Seventeen of 24 samples were evaluable for CD47 expression, including samples from nine of the 10 ccHER2-positive patients. Patients received zanidatamab plus evorpacept at dosages of 20 mg/kg (n=3) or 30 mg/kg (n=21). As of the August 1, 2024 data cut-off, key findings from the analyses include:

The cORR among all 24 patients was 33% and the mPFS was 3.6 months.
Patients with ccHER2-positive disease (n=10) had higher response rates, with a cORR of 60% and mPFS of 8.3 months.
All of the patients (n=5/5) with ccHER2-positive disease and high CD47 expression (defined as total membrane staining of >20%) responded (including one complete response and four partial responses), with an mDOR of 20.2 months and mPFS of 22.1 months. In comparison, among the patients with ccHER2-positive disease and low CD47 expression (defined as total membrane staining of <20%), cORR was 25% (n=1/4) and mPFS was 3.4 months.
"The findings from these exploratory analyses provide additional evidence that adding evorpacept to HER2-targeted therapies may generate durable responses in heavily pretreated HER2-positive breast cancers, including in patients in the post-ENHERTU setting," said Barbara Klencke, M.D., Chief Medical Officer at ALX Oncology. "They also further support the use of a biomarker-driven approach to predict treatment response, as we previously observed in the HER2-positive gastric cancer setting. We designed the ongoing ASPEN-09-Breast Phase 2 trial of evorpacept plus trastuzumab and chemotherapy to provide additional insight into this approach and, we hope, move closer to delivering a new therapeutic option for this group of patients."

Q1 2026 Results Conference Call and Webcast Details

ALX Oncology management will host a webcast tomorrow (Friday, May 8), to provide an overview of Q1 2026 financial results. Sara Hurvitz, M.D., will join the call to discuss and provide perspective on the Phase 1b/2 trial data shared at the ESMO (Free ESMO Whitepaper) Breast Cancer congress.

Date & Time: Friday, May 8, 2026, 8:30 a.m. ET
Guest Speaker: Sara Hurvitz, M.D., Professor, Senior Vice President and Director, Clinical Research Division and Smith Family Endowed Chair in Women’s Health at Fred Hutchinson Cancer Center; Professor and Head, Division of Hematology and Oncology, Department of Medicine, University of Washington
Webcast Access: View Source;tp_key=2800839c82
Participant Listening Options by Phone: To access the conference call, please dial 1-877-407-0752 or +1-201-389-0912 and ask to be joined into the ALX Oncology First Quarter 2026 Financial Results Conference Call.

Another option for instant telephone access to the event is to use the Call Me link below:
View Source;passcode=13755276&h=true&info=company&r=true&B=6

A live audio webcast of the call, along with the ALX Oncology corporate presentation, will be available under "Events & Presentations" in the Investor section of the Company’s website, www.alxoncology.com. An archived webcast will be available on the Company’s website after the event.

(Press release, ALX Oncology, MAY 7, 2026, https://ir.alxoncology.com/news-releases/news-release-details/alx-oncologys-evorpacept-combination-zanidatamab-generates [SID1234665301])