Medpacto, a subsidiary of Theregen ETEX, said Monday that it has presented its phase 1a and 2b clinical trial results on Vactosertib, an immunotherapy agent, at the Society for Immunotherapy of Cancer (SITC) 2019.
Vactosertib is a drug candidate that selectively inhibits transforming growth factor-beta (TGF-β), a mechanism that inhibits the therapeutic effect of immunotherapy.
The research showed that the Vactosertib combination therapy in patients, who were previously ineffective with conventional anticancer drugs alone, showed significant exploratory efficacy on most major clinical indicators.
MedPacto, a developer of biomarker-based innovative new drugs, has been conducting phase 1a and 2b trials in combination with MSD's Keytruda and AstraZeneca's Imfinzi in Korea since last year.
For the combination treatment of Vactosertib and Keytruda, the company is conducting trials at five medical institutions – Asan Medical Center, Samsung Medical Center, Seoul National University Bundang Hospital, Severance Hospital, and National Cancer Center -- for patients with colorectal cancer and gastric cancer. At the SITC 2019, the company announced early results of clinical trials in 14 patients with advanced colorectal and gastric cancer.
In this clinical trial, Medpacto used the treatment on colorectal cancer patients who failed most of the four systemic chemotherapies and had no other treatment options. The company managed to achieve an overall response rate (ORR) of 16.7 percent and 33.3 percent, respectively, based on the primary and secondary anticancer activity evaluation indicators of RECIST and immune RECIST.
Notably, all colorectal cancer patients, who had shown no objective response rate in Keytruda monotherapy, showed a microsatellite-stable (MSS) genotype.
Keytruda had shown an excellent response to microsatellite instability-high (MSI-H) patients, estimated to be less than 20 percent of total colorectal cancer, and had received approval from the U.S. Food and Drug Administration as the first tissue agnostic anticancer drug.
"The trial confirmed the possibility of treating the remaining 80 percent of MSS patients," the company said. "Also, more than half of the patients were treated with the Vactosertib combination therapy showed a decrease in their carcinoembryonic antigen (CEA) levels, which is the tumor markers of colorectal cancer."
This suggests that the overall tumor burden of the patient is effectively reduced with repeated treatment, the company added.
The company also presented the initial clinical trial results of Vactosertib and Imfinzi in 15 patients with non-small cell lung cancer (NSCLC), who had failed platinum-based treatment, at Severance Hospital and the National Cancer Center at the conference.
"Although the trial was conducted in patients aged 66 years of age, who had less than 25 percent PD-L1 expression in tumors which made it difficult to treat them with conventional anticancer drugs alone, we have managed to confirm an ORR of 16.7 percent," the company said.
Considering that the objective response rate of the Imfinzi monotherapy clinical trial in the same patient group was 2.8 percent, the drug dramatically improved treatment outcomes, it added.
Medpacto will continue to conduct the same clinical trials in patients with tumors with more than 1 percent PD-L1 expression and expects to see improved treatment outcomes in the tests as well.
"We have seen encouraging results in most of the indicators, with dramatic improvements in ORR and disease control rates, and a marked decrease in tumor size in the two of the trials," Medpacto CEO Kim Seong-jin said. "Our company has identified the possibility that Vactosertib would give hope to patients who were previously unable to cure with immunotherapy treatments."