ALX Oncology’s Evorpacept in Combination with Zanidatamab Generates Promising, Durable Response in Patients with Advanced HER2-Positive Breast Cancer and High CD47 Expression

Rhea-AI Summary

ALX Oncology (NASDAQ: ALXO) reported Phase 1b/2 exploratory data showing evorpacept plus zanidatamab produced a confirmed objective response rate of 100% (5/5) in ccHER2-positive metastatic breast cancer patients with high CD47 expression (>20%).

High-CD47 patients had mPFS of 22.1 months and mDOR of 20.2 months; low-CD47 patients had mPFS of 3.4 months. A webcast on May 8 will review Q1 2026 results and trial data.

Positive

• ccHER2-positive, high-CD47 cORR of 100% (5/5)
• High-CD47 mPFS of 22.1 months
• High-CD47 mDOR of 20.2 months
• Overall ccHER2-positive cORR of 60% (n=10)

Negative

• Overall cohort mPFS of only 3.6 months
• Exploratory analysis based on small evaluable sample sizes (n=17 for CD47)

News Market Reaction – ALXO

-10.53%

19 alerts

-10.53% Session close to close

+7.1% Peak Tracked

-10.2% Trough Tracked

$282.58M Market Cap

0.8x Rel. Volume

In the May 7 session, ALXO declined 10.53%, reflecting a significant negative market reaction. Argus tracked a peak move of +7.1% during that session. Argus tracked a trough of -10.2% from its starting point during tracking. Our momentum scanner triggered 19 alerts that day, indicating notable trading interest and price volatility.

Data tracked by StockTitan Argus on the day of publication.

Market Context

The stock dropped -10.5% in the session following this news. A negative reaction despite positive bi...

Analysis

The stock dropped -10.5% in the session following this news. A negative reaction despite positive biomarker-driven data would have contrasted with ALXO’s recent tendency for gains after clinical and corporate announcements, where four of the last five events saw positive moves up to 12.07%. Weakness could reflect concerns about small sample size, prior financing overhang, or execution following the earnings event that drew a -10.21% reaction, even as the CD47 strategy progresses.

Key Figures

cORR high CD47: 100% (n=5/5) cORR low CD47: 25% (n=1/4) mPFS high CD47: 22.1 months +5 more

8 metrics

cORR high CD47 100% (n=5/5) ccHER2-positive mBC with CD47 >20% membrane staining

cORR low CD47 25% (n=1/4) ccHER2-positive mBC with CD47 <20% membrane staining

mPFS high CD47 22.1 months ccHER2-positive, high CD47 expression subgroup

mPFS low CD47 3.4 months ccHER2-positive, low CD47 expression subgroup

mDOR high CD47 20.2 months ccHER2-positive, high CD47 expression subgroup

Overall cORR 33% All 24 patients in Phase 1b/2 trial

cORR ccHER2-positive 60% 10 patients with ccHER2-positive disease

Trial size 24 patients Exploratory analyses of Phase 1b/2 evorpacept + zanidatamab

Historical Context

5 past events · Latest: Apr 30 (Positive)

Pattern 5 events

Date	Event	Sentiment	24h Move	Catalyst
Apr 30	Clinical data preview	Positive	+7.6%	Announced upcoming CD47 biomarker data presentation and Q1 2026 call.
Apr 17	Inducement option grant	Neutral	+4.8%	Granted 800,000-share stock option to new development/operating chief.
Apr 13	Executive appointment	Positive	+2.9%	Appointed Jeff Knight as Chief Development and Operating Officer.
Feb 27	Earnings and financing	Positive	-10.2%	Reported FY 2025 results, biomarker advances, and $150M registered offering.
Feb 19	Investor conferences	Neutral	+12.1%	Announced participation in multiple Q1 2026 investor conferences.

24h Move is the share-price change in the day after each event; other market factors may also have contributed.

Pattern Detected

Recent ALXO news has generally seen positive price alignment, with only the earnings/financing update drawing a negative reaction.

Recent Company History

Over the past several months, ALXO has highlighted biomarker-driven development of evorpacept, executive hires, financing, and investor outreach. The Feb 10-K and Feb 27 earnings update emphasized CD47 biomarker data and a capital raise, which saw a -10.21% reaction. Subsequent leadership and conference updates in April produced gains of 2.94–12.07%. The Apr 30 notice about these ESMO biomarker data was followed by a 7.59% move, consistent with today’s clinically focused news.

Key Terms

phase 1b/2, her2-positive, metastatic breast cancer, biomarker-driven, +4 more

8 terms

phase 1b/2 medical

"Data from Phase 1b/2 trial presented at ESMO Breast Cancer 2026..."

Phase 1b/2 is a combined early-stage human study that first checks a drug’s safety and side effects in a small group and then expands to test whether it shows signs of working in patients. Think of it as a product test that first confirms it’s safe to use, then looks for early evidence of benefit; positive results can significantly reduce clinical risk and increase a company’s value, while negative results raise the opposite.

her2-positive medical

"...patients with heavily pre-treated HER2-positive metastatic breast cancer..."

HER2-positive describes cancer cells that have too many copies of the HER2 gene or make too much of the HER2 protein, which acts like an overactive growth switch that drives tumor growth. For investors, HER2 status matters because it determines whether patients can receive specific, often expensive targeted therapies and diagnostic tests, so trial results, approvals, or competing drugs tied to HER2 can strongly affect drug sales and company value.

metastatic breast cancer medical

"...HER2-positive metastatic breast cancer (mBC) were presented..."

Metastatic breast cancer is breast cancer that has spread beyond the breast and nearby lymph nodes to other organs, such as bones, liver, lungs or brain. For investors it matters because these advanced-stage cases often require long-term, complex and costly treatments, drive demand for specialty drugs and diagnostics, and influence regulatory approvals, pricing negotiations and the long-term revenue potential of companies developing therapies aimed at slowing spread or improving quality of life. An everyday analogy: it’s like a weed that has taken root in multiple beds rather than just one garden patch, requiring broader and more sustained effort to manage.

biomarker-driven medical

"...validate a biomarker-driven development strategy for evorpacept..."

An approach where medical decisions—like choosing patients for a treatment or designing a clinical trial—are guided by measurable biological signs (such as a gene change, protein level, or imaging result). For investors, biomarker-driven programs can raise the odds of clinical success, shrink development costs and speed regulatory review by targeting therapies to the people most likely to benefit, much like using a map to find the best route instead of driving aimlessly.

objective response rate medical

"...had a confirmed objective response rate (cORR) of 100% (n=5/5)..."

The objective response rate (ORR) is the percentage of patients in a clinical trial whose tumors measurably shrink or disappear according to preset rules. Investors use it as a quick, objective signal of a drug’s ability to produce a clear treatment effect—like counting how many plants visibly respond after applying a new fertilizer—and higher ORR can improve odds of regulatory approval, commercial success, and company valuation.

progression-free survival medical

"Those patients whose tumors expressed higher levels of CD47 also had longer median progression-free survival (mPFS)..."

Progression-free survival is the length of time during and after a treatment that a patient's disease does not get worse, measured from the start of treatment until the disease shows measurable signs of progression or the patient dies. Investors care because longer progression-free survival in clinical trials often signals that a drug is effective, improving chances of regulatory approval, market adoption, and revenue potential—think of it as a stopwatch showing how long a therapy can keep the illness at bay.

duration of response medical

"The median duration of response (mDOR) among patients whose tumors expressed high levels of CD47..."

Duration of response is the length of time a patient’s condition stays improved after a treatment until it starts to worsen again; think of it as how long a freshly charged battery continues to power a device. For investors, longer duration of response implies a treatment provides sustained benefit, which can boost a drug’s commercial value, support stronger regulatory labeling and payer coverage, and reduce the need for additional therapies.

open-label medical

"The Phase 1b/2 open-label, multi-center clinical trial (NCT05027139)..."

Open-label describes a situation where everyone involved in a study or process knows the full details, such as who is receiving a treatment or intervention. For investors, understanding whether a project or product is open-label helps gauge the level of transparency and potential biases, influencing trust and decision-making. It’s like knowing whether a test or experiment is conducted openly or behind closed doors.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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- Data from Phase 1b/2 trial presented at ESMO Breast Cancer 2026 further validate a biomarker-driven development strategy for evorpacept -

- Findings are consistent with previous results from the randomized ASPEN-06 trial in HER2-positive gastric cancer, which indicated CD47 expression could potentially serve as an important predictive biomarker of evorpacept activity -

- ALX Oncology will host a webcast on May 8 to report first quarter 2026 financial results; breast cancer expert will discuss the evorpacept + zanidatamab trial results in detail -

SOUTH SAN FRANCISCO, Calif., May 07, 2026 (GLOBE NEWSWIRE) -- 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, announced 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 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.

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 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: https://viavid.webcasts.com/starthere.jsp?ei=1758590&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:
https://callme.viavid.com/viavid/?callme=true&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.

About ALX Oncology
ALX Oncology (Nasdaq: ALXO) is a clinical-stage biotechnology company advancing a pipeline of novel therapies designed to treat cancer and extend patients’ lives. ALX Oncology’s lead therapeutic candidate, evorpacept, has demonstrated potential to serve as a cornerstone therapy upon which the future of immuno-oncology can be built. Evorpacept is currently being evaluated across multiple ongoing clinical trials in a wide range of cancer indications. ALX Oncology’s second pipeline candidate, ALX2004, is a novel EGFR-targeted antibody-drug conjugate with a differentiated mechanism of action. A Phase 1, dose-escalation trial of ALX2004 is ongoing in patients with EGFR-expressing solid tumors. More information is available at www.alxoncology.com and on LinkedIn.

Cautionary Note Regarding Forward-Looking Statements
This press release contains forward-looking statements that involve substantial risks and uncertainties. Forward-looking statements include statements regarding future results of operations and financial position, business strategy, product candidates, planned preclinical studies and clinical trials, results of clinical trials, research and development costs, regulatory approvals, timing and likelihood of success, plans and objects of management for future operations, as well as statements regarding industry trends. Such forward-looking statements are based on ALX Oncology’s beliefs and assumptions and on information currently available to it on the date of this press release. Forward-looking statements may involve known and unknown risks, uncertainties and other factors that may cause ALX Oncology’s actual results, performance or achievements to be materially different from those expressed or implied by the forward-looking statements. These and other risks are described more fully in ALX Oncology’s filings with the Securities and Exchange Commission (“SEC”), including ALX Oncology’s Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q and other documents ALX Oncology files with the SEC from time to time. Except to the extent required by law, ALX Oncology undertakes no obligation to update such statements to reflect events that occur or circumstances that exist after the date on which they were made.

Investor Relations Contact:
Elhan Webb, CFA, IR Consultant
ewebb@alxoncology.com

Media Contact:
Michele Parisi, SparkPoint Healthcare Communications
mparisi@sparkpointpr.com
(925) 864-5028

FAQ

What did ALXO announce about evorpacept plus zanidatamab at ESMO Breast Cancer 2026?

The combination produced a 100% confirmed response in ccHER2-positive patients with high CD47 (5/5). According to ALX Oncology, high-CD47 tumors showed a median PFS of 22.1 months and median DOR of 20.2 months in exploratory analyses.

How many ALXO trial patients had high CD47 and what were their outcomes?

Five ccHER2-positive patients had high CD47 expression and all responded (5/5). According to ALX Oncology, responses included one complete and four partial responses, with an mDOR of 20.2 months and an mPFS of 22.1 months.

What were the outcomes for ALXO patients with low CD47 expression in the trial?

Patients with low CD47 had a confirmed ORR of 25% and shorter PFS. According to ALX Oncology, among ccHER2-positive low-CD47 patients (n=4) cORR was 25% and mPFS was 3.4 months in the exploratory dataset.

Will ALX Oncology discuss these results and when is the Q1 2026 webcast for ALXO?

ALX Oncology will host a webcast on May 8, 2026 at 8:30 a.m. ET to review Q1 2026 results and trial data. According to ALX Oncology, the event includes expert commentary and will be available via live audio webcast and archived online.

How large was the evaluable CD47 sample and what trial supports ALXO's biomarker approach?

Seventeen tumor samples were evaluable for CD47, including nine ccHER2-positive cases. According to ALX Oncology, these exploratory results align with prior ASPEN-06 gastric cancer findings supporting CD47 as a predictive biomarker for evorpacept activity.