Merus announced something amazing recently, and this was with respect to released interim data from its phase 2 trial using its bispecific antibody petosemtamab in combination with pembrolizumab (KEYTRUDA) for the treatment of patients with first-line recurrent/metastatic (r/m) head and neck squamous cell carcinoma (HNSCC). This data comes ahead of an expected presentation that is going to be done at the upcoming 2025 American Society of Clinical Oncology (ASCO) Annual Meeting on Monday, June 2, from 9 a.m. to 12 p.m. CT.
With a cutoff date of February 27th of 2025, interim data was revealed for a total of 45 first-line PD-L1+ (positive) recurrent/metastatic HNSCC patients. It was noted that a total of 27 out of 43 (63%) of patients responded to the therapy. This is a good response rate, but what was even more pronounced was the overall survival (OS) data that was achieved. It was noted that the OS rate at 12 months was 79%. This data is highly encouraging because these particular solid tumor patients have a high mortality rate and limited treatment options. Consider that the current standard of care (SOC) for these HNSCC patients is KEYTRUDA monotherapy.
The data release only stemmed from the ongoing phase 2 study using the petosemtamab combination to treat these patients. The company is already in the process of running two phase 3 studies for this program targeting these HNSCC patients. The phase 3 LiGeR-HN1 study is targeting first-line r/m patients, and then the phase 3 LiGeR-HN2 study is targeting patients who are 2nd-line/3rd-line r/m. It is making significant progress with both of these late-stage trials, as it believes it is on track to complete enrollment for both by the end of 2025. Having said that, with this projection staying on track, it believes it could release interim data from one or both of these trials in 2026. This would definitely provide further upside for the share price if the data is replicated to what has been shown from this ongoing phase 2 study.
What makes petosemtamab stand out for the company as a bispecific EGFR/LGR5 antibody is that it is versatile and can be applied to several other solid tumor types. With that being said, it is also evaluating the use of this drug in combination with standard chemotherapy to treat first-line, second-line, and third-line metastatic colorectal cancer (mCRC). Initial data from this mid-stage study is expected to be released at some point in the second half of 2025 and could provide another major inflection point for this drug candidate.
Merus’ technology is intriguing, and it involves its Multiclonics proprietary technology platform, which is able to generate a multitude of different binding domains against any target. This is further broken down into Biclonics (dual-targeting effect), Triclonics (triple targeting), and ADclonics (antibody-drug conjugates) capable of binding to two targets for enhanced selectivity and potency. In the case of petosemtamab, this falls under the Biclonics development program of the Multiclonics platform. Its dual targeting is that of a well-established EGFR target and LGR5. In terms of EGFR, it is a mutation that causes cell growth and division in cancer. From there, LGR5 is known to be able to allow cancer to survive through cell migration, angiogenesis, and invasion. Plus, it could also be a boost for being involved with metastasis of the tumor. All that remains now is to see whether or not the interim data shown can be replicated in the ongoing phase 3 LiGeR studies.
Head and neck squamous cell carcinoma is, as the name suggests, where there is the growth of malignant cells in the head/neck area of a patient. The problem, though, is that these patients face something even more dire, which is recurrence. That is, despite being treated with standard of care (SOC) therapies, their cancer tends to recur or come back. The type of treatments that a patient might face could be that of surgery, chemotherapy, or a combination of a few treatment types.