Altered Herpes Virus Halts Mesothelioma Growth in New Study

An altered herpes virus has been shown to stabilize the growth of mesothelioma tumors in half of patients who participated in a new UK study. 

Researchers at the University of Sheffield injected thirteen mesothelioma patients with a cancer cell-seeking version of HSV, the virus that causes herpes. 

The altered herpes virus is not able to replicate in non-dividing cells. This also makes it most destructive inside cancer cells. It is also attenuated or weakened so it does not cause herpes.

Other studies show the virus (HSV1716) can stimulate the immune system against cancer. The new report suggests that it may be a safe new way to fight mesothelioma, too.

The Need for a New Mesothelioma Drug

The FDA has only approved two drug therapies for mesothelioma since the disease was first identified around the 1930s. The first is the chemotherapy drug Alimta approved in 2004. The second is a combination of Opdivo and Yervoy approved earlier this year. 

If the altered herpes virus proves to be safe and effective, it could form the basis of a new mesothelioma drug treatment. It might even make existing treatments more effective. 

At best, current treatments may shrink pleural mesothelioma tumors by a little bit. At worst they can cause serious side effects and may not work at all. Alternative treatments for mesothelioma are urgently needed. 

Testing the Altered Herpes Virus for Mesothelioma

The UK study enrolled 13 patients with malignant pleural mesothelioma to test the altered herpes virus. Five patients already had chemotherapy with Alimta. Eight had not had any chemotherapy yet. Mesothelioma surgery was not an option for any of these patients.

Patients received the treatment through a pleural catheter. This allowed doctors to inject the altered herpes virus directly into the space where mesothelioma tumors grow. Three of the study subjects got one dose, three patients got two doses, and seven patients received four doses. 

“The treatment was well-tolerated with few virus-related adverse events and no dose limiting toxicities,” reports study author Sarah Danson. Tests showed that the treatment also stimulated the patients’ immune systems to help fight their mesothelioma.

Unfortunately, HSV1716 did not shrink any of the mesothelioma tumors. But it did stop tumors from growing in half of the patients for two full months. 

The researchers conclude that this altered herpes virus “demonstrated an anti-tumor immune response” in pleural mesothelioma patients. 

“These results provide a rationale for further studies with this agent in MPM and in combination with other therapies,” writes Dr. Danson.

Sources:

Canson, S, et al, “Oncolytic herpesvirus therapy for mesothelioma – A phase I/IIa trial of intrapleural administration of HSV1716”, October 20, 2020, Lung Cancer, Epub ahead of print, https://linkinghub.elsevier.com/retrieve/pii/S0169500220306590