Doctors on Saturday praised "unprecedentedly strong responses” to an injection that eradicated entire tumors in otherwise treatment-resistant cancer cases during a trial.
It shrank the tumors for 42% of patients in the study by the Institute of Cancer Research (ICR), London.
Scientists gave amivantamab to people with recurrent and/or metastatic head and neck cancer that had stopped responding to standard treatments.
Amivantamab is a small injection, unlike many cancer medications that require intravenous drips.
One participant with tongue cancer said the treatment reduced his pain and swelling and he is no longer experiencing the "life-impacting” side effects he had during chemotherapy.
Professor Kevin Harrington, professor in biological cancer therapies at the institute and consultant oncologist at The Royal Marsden NHS Foundation Trust, said: "These are unprecedentedly strong responses in patients whose disease has become resistant to both chemotherapy and immunotherapy.
"This is a group of patients for whom treatment options are extremely limited, so seeing this level of benefit is very striking.”
He added: "This treatment has the potential to benefit many thousands of patients each year.”
Head and neck cancer is the sixth most common cancer worldwide and it affects around 12,800 people in the U.K. each year.
This phase of the OrigAMI-4 trial looked at 102 people with recurrent or metastatic head and neck squamous cell carcinoma (HNSCC), whose cancer had continued to grow despite immunotherapy and platinum-based chemotherapy.
The patients, from 55 hospitals in 11 countries, only received amivantamab, which is being developed by Johnson & Johnson.
Tumors shrank in 43 participants, 15 had them disappear completely and 28 saw their tumors shrink significantly.
Patients with amivantamab lived for a median of 12.5 months after starting the treatment, despite having a cancer type with "very poor outcomes” once standard treatments stop working, the ICR said.
Tumors started to respond within about six weeks and patients had a median of a little more than six-and-a-half months before the cancer started to grow again, it found.
Carl Walsh, 56, from Birmingham, was diagnosed with tongue cancer in May 2024 and joined the study at The Royal Marsden in July 2025 after chemotherapy and immunotherapy were both unsuccessful.
In a statement released by the ICR during his 17th treatment cycle, he said: "I now feel able to live a normal life. Before starting the trial, I struggled to speak properly and found eating difficult because of the swelling and pain.
"Since beginning treatment, the swelling has reduced significantly, and my pain levels have improved considerably.
"I’m also no longer experiencing the same life-impacting side effects that I had during chemotherapy.”
The drug is called a bispecific monoclonal antibody and it blocks two signals: the epidermal growth factor receptor (EGFR), which is a protein that helps tumors grow, and MET, a separate pathway often used by cancer cells to escape treatment.
It also has a third benefit: helping to activate the immune system to attack the tumor.
The fact it is an injection makes it faster, more convenient for patients, and "significantly easier” to deliver in outpatient clinics, the ICR said.
Amivantamab is given every three weeks and side effects were mild to moderate.
Fewer than 10 patients stopped treatment because of side effects.
Professor Kristian Helin, chief executive of the ICR, said: "This study demonstrates how the development of new treatments through rigorous cancer research may lead to meaningful advances, even for patients with very limited treatment options.
"Achieving this level of tumor response and encouraging survival outcomes in such a challenging-to-treat group represents a significant step forward.”
Amivantamab has already been approved for multiple subtypes of lung cancer across multiple lines of therapy.
The study excluded patients who had human papillomavirus (HPV) positive oropharyngeal squamous cell carcinoma.
Head and neck cancers that are not caused by HPV are usually harder to treat and have poorer responses to standard therapy, ICR said.
"Making progress in this group particularly important,” the institute added.
The study is being presented to the American Society of Clinical Oncology on Sunday.
