CStone Pharmaceuticals has collaborated with Bayer HealthCare to study the combination of its investigational drug CS1001 with Bayer’s regorafenib to treat various cancers, including gastric cancer.

CS1001 is a PD-L1 monoclonal antibody, while regorafenib is a multi-kinase inhibitor.

Under the worldwide clinical alliance, the companies will conduct a proof of concept study to assess the combination therapy’s safety, tolerability, pharmacokinetics (PK), and anti-tumour activity.

The clinical programme will be funded by CStone and Bayer will supply regorafenib.

CStone Pharmaceuticals chairman and CEO Dr Frank Jiang said: “We hope, by complementing our two companies’ pipelines via this combination therapy, that we can develop better cancer treatments for patients. In addition, this collaboration will be a big step forward for CStone’s global strategy when we generate positive data.”

CS1001, which is part of CStone’s immuno-oncology pipeline, has demonstrated favourable tolerability profile and anti-tumour activities across different tumour types in clinical studies.

The drug candidate is currently undergoing seven clinical trials, including five pivotal trials.

These studies comprise a Phase I trial in the US, a multi-arm Phase Ib study, two pivotal Phase II studies and three Phase III trials in China.

Regorafenib holds approval for metastatic colorectal cancer (mCRC) and metastatic gastrointestinal stromal tumours (GIST) in more than 90 countries, and as second-line therapy of advanced hepatocellular (HCC) in more than 80 countries.

Bayer Pharmaceutical division senior vice-president and Oncology Development head Scott Fields said: “Combining multi-kinase inhibitors, such as regorafenib, with checkpoint inhibitors is a rising trend in cancer therapy in order to find new solutions for the many treatment gaps that still remain for patients.”

Bayer entered an agreement in 2011, which will see Onyx will receive a royalty on all global net sales of regorafenib in oncology.