CAP7.1 – Suitable for the treatment of Biliary Tract Cancer and Gallbladder Cancer
CAP7.1 is an inactive precursor of the already well-known chemotherapeutic agent etoposide. However, CAP7.1 has been designed to create a more targeted treatment approach, e.g. for the treatment of gallbladder cancer and biliary tract cancer. CAP7.1 is administered intravenously but remains inactive because the active substance, etoposide, is ‘disguised’. Etoposide is slowly released in the body by a special enzyme called carboxylesterase. This enzyme is expressed in normal tissues and exhibits a particularly high biological activity in different tumour cells. The release of etoposide, therefore, seems to happen more frequently in the areas of cancer cells. This mechanism allows good tolerability of CAP7.1 at relatively high doses and also revealed efficacy in the treatment of refractory tumors including those previously treated with etoposide. A particularly high expression of carboxylesterase in gastrointestinal tissue, especially in the liver, could also indicate that CAP7.1 is particularly suitable for patients with biliary tract carcinomas.
When chemotherapy is not effective, this is likely caused by the development of multidrug resistance (MDR) i.e., multiple resistance of the cancer against anti-cancer drugs. Research results indicate that CAP7.1 is not affected by existing MDR because of its different type of molecular activity. Hence, CAP7.1 may not be subject to the same limitations as other anti- cancer drugs.
CAP7.1: First Studies on Safety and Efficacy
At the Charité University Hospital, Berlin, Germany, in 2012, a phase I study was completed with 19 adult patients with various solid tumours. The majority of patients tolerated treatment with CAP7.1 well. Eleven patients had stable disease over a period of six months. Reduction in tumour mass was observed in a few patients. One patient showed a partial remission. The longest survival times were seen in patients with biliary tract carcinoma and non-small cell lung cancer. The results suggest a dose related effect, in particular in gastrointestinal malignancies, such as in the stomach, gall bladder and esophagus, but also in ovarian, testicular, head and neck, and lung cancers.
In 2003, CAP7.1 was tested in children. In the study (Compassionate Trial), the three pediatric patients with stage 4 neuroblastoma were treated with CAP7.1 in combination with carboplatin and showed good tolerability, without organ toxic side effects. In 2 of 3 children, a remission over a period of several months was achieved.