• In ASPEN-03 and ASPEN-04 trials, efficacy data do not support advancing evorpacept in combination with Merck's anti-PD-1 therapy, KEYTRUDA® (pembrolizumab), into a registrational study
• Company remains confident in continuing to pursue evorpacept in multiple clinical trials, based on the different mechanism of evorpacept in combination with anti-cancer antibodies, as evidenced by durable clinical response and consistent safety data in prior clinical trials
  
  ALX Oncology Holdings Inc., ("ALX Oncology" or the "Company") (NASDAQ:ALXO), a clinical-stage biotechnology company advancing a pipeline of novel therapies designed to treat cancer and extend patients' lives, today announced topline data from its Phase 2 ASPEN-03 and ASPEN-04 clinical trials. The company's investigational CD47-blocker evorpacept, when added to Merck's (known as MSD outside of the US and Canada) anti-PD-1 therapy, KEYTRUDA® (pembrolizumab) with or without chemotherapy, did not meet the primary endpoints in the ASPEN-03 and ASPEN-04 trials of improved objective response rates (ORR) as compared to historical controls of pembrolizumab alone and pembrolizumab with chemotherapy, respectively, as a first-line treatment in patients with advanced head and neck squamous cell carcinoma (HNSCC). The combination of evorpacept and pembrolizumab with or without chemotherapy in ASPEN-03 and ASPEN-04 demonstrated a manageable safety profile and was consistent with what has been previously reported for pembrolizumab and chemotherapy in this setting. Although the company will no longer pursue evorpacept in combination with pembrolizumab in HNSCC, multiple clinical trials of evorpacept in combination with anti-cancer antibodies will continue based on established proof-of-concept.

Evorpacept blocks the ‘don't eat me' signal transmitted by CD47 on the surface of cancer cells that these cells use to evade detection by the immune system. As its primary mechanism of action, evorpacept is uniquely designed to stimulate macrophages to selectively attack cancer cells and not healthy cells, when combined with active anti-cancer antibodies. This mechanism has translated into durable clinical responses and a well-tolerated safety profile in HER2-positive gastric and HER2-positive breast cancer clinical trials. To further explore the benefit in this setting, evorpacept is currently being evaluated in combination with various anti-cancer antibodies in colorectal cancer, breast cancer, non-Hodgkin lymphoma and multiple myeloma.

In the ASPEN-03 and ASPEN-04 clinical trials, evorpacept was combined with pembrolizumab with or without chemotherapy to investigate a second and distinct mechanism of action. This discrete approach explored the concept that evorpacept may enhance T-cell priming by activating dendritic cells and stimulating the adaptive immune system. The trial outcomes were not sufficiently supportive of advancing evorpacept in combination with pembrolizumab in HNSCC into a registrational trial.

"While there were encouraging trends in ASPEN-03 in ORR versus the historical and internal control, we've decided not to pursue evorpacept and pembrolizumab in head and neck cancer in light of our prioritization of the more established anti-cancer antibody combination program based on multiple positive studies," said Alan Sandler, M.D., Chief Medical Officer at ALX Oncology. "We are disappointed that these studies did not meet their primary endpoints, most importantly for the patients for whom current standard-of-care treatment approaches fall short, and we thank all who participated in the trials."

"Moving forward, we are continuing to rapidly advance our clinical program combining evorpacept with anti-cancer antibodies supported by robust clinical data across trials in multiple tumor types. Evorpacept has demonstrated response rates and durability beyond what is expected from standard of care across several studies when combined with HERCEPTIN®, zanidatamab and RITUXAN®," said Jason Lettmann, Chief Executive Officer at ALX Oncology. "Based on the positive data and strong mechanistic rationale, we maintain our confidence in the evorpacept clinical development program and intend to deliver on that promise with additional clinical data in breast cancer and colorectal cancer in the near-term. With evorpacept and ALX2004, our novel EGFR-targeted antibody-drug conjugate, we continue our commitment to bringing forth meaningful therapies for patients living with cancer."