Early Success Reported for New Mesothelioma Vaccine

Researchers in Scotland are developing a mesothelioma vaccine designed to kill tumors after the disease begins.

The vaccine infects mesothelioma cells with the virus. What is intriguing is that the virus is programmed to infect mesothelioma cells only. It has no interest in attacking cells.

Details of the virus were shared by the researchers through a pair of science posters they published and then presented at the Society for ImmunoTherapy of Cancer annual meeting in early November.

Using an Oncolytic Virus to Attack Mesothelioma

The vaccine is called Seprehvir. It’s being developed Virttu, a company that specializes in oncolytic viruses.

Oncolytic viruses are those that only target and infect cancer cells. Seprehvir started out as a common human virus but was then modified in the lab to have an affinity for cancer cells like mesothelioma.

Once an oncolytic virus finds and infects a cancer cell, it also causes the body’s immune system to unleash an armada of macrophages. Those are white blood cells that naturally try to destroy any viruses that penetrate your body.

Since the oncolytic virus is contained within the cancer cell when the macrophages arrive, both the virus and host cancer cell are attacked as a single unit.

The company’s researchers have so far treated nearly 100 patients with Seprehvir. Not all of them have been mesothelioma patients, though. Some have had skin cancers, brain cancers and neuroblastomas.

The researchers have seen encouraging results with all those cancers and several others. These results were discussed in the first presented poster, “Immune responses following intrapleural administration of oncolytic HSV Seprehvir in patients with malignant pleural mesothelioma.”

The poster describes results from the company’s ongoing clinical trial of Seprehvir. That study offered data from an analysis of sequential pleural fluid samples taken after Seprehvir had been given.

Those samples revealed “a robust Th1 cytokine response and the appearance of novel anti-tumor IgG responses in most treated patients.” The researchers said this represented solid evidence that Seprehvir may be effective.

MRI Guide Viruses to Mesothelioma

Poster 2, “Use of magnetic resonance targeting to steer OV-loaded cell-based therapies to tumour sites in vivo,” discussed the technique of using an MRI machine to paint the tumor targets — to light them up so that that virus has no trouble finding them.

This wasn’t tested on humans. It was just a simulation in the lab. But it built on research a colleague conducted using an orthotropic, metastatic prostate cancer model.

This model employed magnetic nanoparticles. The nanoparticles were loaded up with Seprehvir. MRI was then used to pull the nanoparticles to the target cells.

Interestingly, the nanoparticles do not carry the vaccine directly to the cancer cells. Instead what happens is the nanoparticles attach to macrophages and are carried to the destination by the macrophages.

This has the effect of transforming the macrophages “from a benign, quiescent form to an aggressive anti-cancer-type associated with tumor rejection,” according to the researchers.

The researchers note that Seprehvir can be administered by whatever method works best for the type of cancer being targeted. The options include intravenous infusion, direct intratumoral injection, and loco-regional infusion.

The company’s two posters were also published as abstracts in the Journal for ImmunoTherapy of Cancer.