Phanes' Spevatamig Aims to Solve Cancer Drug Toxicity Puzzle

SAN DIEGO, CA – March 18, 2026 – Clinical-stage biotech company Phanes Therapeutics is set to present compelling new data on its lead cancer drug, spevatamig, potentially signaling a breakthrough in treating difficult gastrointestinal cancers while solving a critical safety issue that has plagued a promising class of immunotherapies. The company announced it will unveil three posters at the upcoming American Association for Cancer Research (AACR) 2026 conference in San Diego this April.

The presentations will feature updated results from the ongoing Phase 2 clinical trial of spevatamig (PT886), a first-in-class bispecific antibody. This innovative drug is designed to simultaneously engage two separate targets on cancer cells, claudin 18.2 (CLDN18.2) and CD47, a dual-action mechanism that is showing promise not only in efficacy but also in patient tolerability.

A Dual-Pronged Attack on Cancer

Spevatamig represents a sophisticated strategy in the war on cancer. Its power lies in its bispecific design, allowing it to act as a molecular bridge that executes a two-pronged attack. One arm of the antibody targets CLDN18.2, a protein frequently found on the surface of tumor cells in hard-to-treat cancers like pancreatic, gastric, and gastroesophageal junction (GEJ) adenocarcinomas, but largely absent from healthy tissues. This makes it an attractive bullseye for targeted therapies. The current benchmark for this target, zolbetuximab, has already demonstrated the clinical value of honing in on CLDN18.2.

The other arm of spevatamig targets CD47, a protein often called the “don’t eat me” signal. Cancer cells exploit CD47 to protect themselves from being engulfed and destroyed by macrophages, a type of immune cell. By blocking this signal, anti-CD47 therapies effectively remove the cancer cells' invisibility cloak, unleashing the immune system to attack the tumor. This mechanism is thought to kill tumor cells through macrophage-mediated phagocytosis (ADCP) and also activate other immune cells, such as NK cells, for a broader anti-tumor response.

By combining these two targets, spevatamig aims to achieve a synergistic effect. It not only flags cancer cells for destruction via the CLDN18.2 target but also simultaneously disables their primary defense mechanism against the immune system, potentially leading to a more potent and durable anti-cancer effect than targeting either pathway alone.

Solving the CD47 Safety Puzzle

While the potential of targeting CD47 is immense, its development has been fraught with challenges. The primary hurdle has been significant hematological toxicity. Because CD47 is also present on the surface of healthy red blood cells and platelets, early-generation anti-CD47 drugs often caused these healthy cells to be destroyed, leading to severe anemia and thrombocytopenia. This on-target, off-tumor effect has been a dose-limiting factor and led to setbacks for several programs, including the discontinuation of a Phase 3 trial for magrolimab, one of the pioneering drugs in the class.

Phanes Therapeutics believes it has engineered a solution to this problem. One of its upcoming AACR posters is titled, "Resolved hematological toxicities associated with anti-CD47 agents using a bispecific design involving an optimized anti-CD47 arm." This points directly to the company's key innovation: a specially designed anti-CD47 component that demonstrates minimal binding to human red blood cells while retaining strong binding to CD47 on tumor cells. This preferential targeting is designed to spare healthy blood cells, thereby mitigating the dangerous side effects that have hindered other therapies.

This claim is supported by early clinical data. At the ASCO Gastrointestinal Cancers Symposium in January 2026, Phanes reported that patients treated with spevatamig in combination with chemotherapy showed no severe (Grade ≥ 3) treatment-emergent anemia, neutropenia, or thrombocytopenia. The rates of these side effects were comparable to those seen with chemotherapy alone, providing a powerful clinical proof-of-concept for the safety of its unique design.

Promising Efficacy and Improved Patient Experience

Beyond its improved safety profile, spevatamig is also demonstrating encouraging anti-tumor activity. The data presented at ASCO GI from the TWINPEAK study focused on its use as a first-line treatment for metastatic pancreatic ductal adenocarcinoma (mPDAC), one of the most lethal cancers with limited treatment options. In a cohort of 15 patients, the combination of spevatamig with standard chemotherapy achieved a 93% disease control rate and a 40% objective response rate. The median progression-free survival was 7.3 months, and the median overall survival stood at a promising 13.2 months and was still maturing.

These results are particularly significant given that 85% of screened pancreatic cancer patients were found to have tumors positive for the CLDN18.2 target, suggesting a broad potential patient population. The focus on patient quality of life is further underscored by another AACR poster, which will detail spevatamig's ability to reduce nausea and vomiting—debilitating side effects that often compromise a patient's ability to continue treatment.

This dual focus on potent efficacy and enhanced tolerability addresses a critical unmet need in oncology: developing treatments that are not only effective but also allow patients to maintain a better quality of life during their fight against cancer.

Strategic Validation and a Growing Pipeline

The progress of spevatamig has not gone unnoticed. The U.S. Food and Drug Administration (FDA) has granted the drug Orphan Drug Designation for pancreatic cancer and, more recently, Fast Track designation for CLDN18.2-positive metastatic pancreatic adenocarcinoma. These designations are intended to expedite the development and review of drugs that treat serious conditions and fill an unmet medical need.

Further validating the drug's potential is a 2023 clinical collaboration agreement with pharmaceutical giant Merck. Under the agreement, Phanes is studying spevatamig in combination with Merck's blockbuster anti-PD-1 therapy, KEYTRUDA® (pembrolizumab), for patients with gastric or GEJ cancers. This partnership combines two powerful immuno-oncology mechanisms and represents a significant vote of confidence from an established industry leader.

Spevatamig is the lead asset in Phanes' wholly-owned portfolio of differentiated antibody therapeutics. The San Diego-based company is also advancing two other programs in clinical trials: peluntamig, a bispecific antibody for small cell lung cancer, and mavrostobart, a monoclonal antibody targeting CD73. The upcoming presentations at AACR will provide a deeper look into the pharmacokinetics and clinical benefits of spevatamig. The full data to be unveiled in April will be closely watched by the oncology community for confirmation of the drug's potential to redefine treatment for these challenging malignancies.