SillaJen said Pexa-Vec, an oncolytic viral drug, still had significant potentials despite the recent failure of the global phase-3 liver cancer trial.

Even though the company failed to prove the experimental treatment’s efficacy in a combination treatment with targeted therapy, using Pexa-Vec with immunotherapy showed positive results, including complete remission, the company said.

SillaJen held an urgent press conference at the CCMM Building in Yeoeui-do, Seoul, on Sunday and disclosed partial data of a study on the combo therapy of Pexa-Vec and an immune checkpoint inhibitor.

“We ended the phase-3 trial for liver cancer earlier than expected, but the study was just one of SillaJen’s numerous trials, either in progress or to be conducted,” SillaJen’s Chief Medical Officer Kwon Hyuk-chan said.

The company had to scrap the phase-3 PHOCUS trial, in which it aimed to confirm if the combination Pexa-Vec and Nexavar (sorafenib), a targeted therapy, can reduce risks for liver cancer patients, compared to Nexavar alone. The group treated with the combo failed to improve overall survival, compared to the control group.

SillaJen CEO Moon Eun-sang (center) and Chief Medical Officer Kwon Hyuk-chan (second from right) hold a news conference at the CCMM Building in Yeoeui-do, Seoul, on Sunday.

However, Pexa-Vec works better with immunotherapy, rather than with targeted therapy, according to Kwon.

He introduced three cases where the drug showed high efficacy when used with Libtayo for metastatic renal cell cancer. Libtayo is immunotherapy jointly developed by Regeneron and Sanofi.

Kwon said a Korean patient with multiple metastases to the lung after renal cancer surgery witnessed the disappearance of tumor tissues around the lung at the ninth and 18th week after the combo treatment. After receiving the first dose in July last year, the patient has demonstrated no additional symptoms until now.

A Caucasian patient whose renal cancer relapsed and spread to multiple organs also showed complete remission after the combo therapy.

“It is significantly meaningful that a Caucasian, not an Asian, had a complete remission. When we discuss licensing-out deals, this case will become an important example,” Kwon emphasized.

He also mentioned a case of delay response. One patient had tumor grown at the ninth week and was regarded as non-responding, but the tumor shrank at the 18th week, he said.

“Unlike conventional anticancer drugs, immunotherapy sometimes shows a delay response, with a rare probability of less than 5 percent,” he added.

In a trial sponsored by the U.S. National Cancer Institute (NCI), one patient showed a partial response of a reduced tumor, and another, a complete response, according to Kwon.

“Some critics say a single case cannot mean much. But we will collect various cases and present them at the Gastrointestinal American Society of Clinical Oncology (GI ASCO) in January,” he said.

The company also unveiled plans for trials on Pexa-Vec’s combination with immunotherapies at the press conference.

SillaJen will work on a combo of Pexa-Vec and MSD(Merck in the U.S.)’s Keytruda for patients with breast cancer whose tumor spread to the liver. For patients with pancreatic cancer, biliary cancer, gastric cancer whose disease spread to the liver, it will test the combo of Pexa-Vec with BMS’ Opdivo.

“We will start the breast cancer trial at five local hospitals and register the first patient in the first quarter of next year. If we see a response, even if it is a little bit, we will expand the trial in the U.S. and clinch a deal with Merck with the earned data,” Kwon said. “We have our protocol already planned for digestive organ cancer with a combo of Pexa-Vec and Opdivo.”

SillaJen also aims to prove Pexa-Vec’s effectiveness with a neoadjuvant therapy that reduces the size of the tumor before surgery.

The company conducted Pexa-Vec neoadjuvant therapy on six patients with colon cancer and three with melanoma. One is likely to show complete necrosis, and another, partial necrosis, the company said.

SillaJen is to unveil the data of the neoadjuvant therapy in nine patients at the Congress of the European Society for Medical Oncology next month.

However, it is expected to take a long time to see the study results due to the difficulty in recruiting patients. For a renal cancer trial, the company has recruited only 11 patients out of the target of 89. As the two immunotherapies are reimbursable, patients rarely apply for a new clinical trial.

“Two immunotherapies are reimbursable already, and big pharmaceutical firms are competing to conduct many combo therapy trials in renal cancer. So, we are working on our trials under a tough situation,” Kwon said. “It is difficult to provide a precise timeline when we will have the trial results.”

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