Phase I study of intrathecal chemotherapy with NS-101 for leptomeningeal carcinomatosis in Japan

Intrathecal administration of MTX and/or Ara-C through the Ommaya system placed in a ventricle has been accepted as a standard therapy for leptomeningeal carcinomatosis. Recently, sustained-release cytosine arabinoside, a depot cytosine arabinoside liposomal injection: DepoCyt, has been reported to be useful for the treatment of leptomeningeal carcinomatosis in Canada, Europe, and the USA. Phase I study of NS-101, DepoCyt in Japan, was performed in patients with leptomeningeal carcinomatosis from solid tumors using the continuous reassessment method (CRM). NS-101 was administered twice through the Ommaya system placed in the lateral ventricle with an interval of 2 weeks. A dose of 25 mg was initially tried in a patient and then a dose of 50 mg was administered in 8 patients. The recommended dose of NS-101 was estimated from pharmacodynamics and tolerance from CRM, and the clinical effectiveness of NS-101 was also assessed. We also compared the present data with the reported data from Europe and the USA. As a result, free Ara-C was maintained over the estimated effective concentration for 2 weeks, and no pharmacodynamic differences were confirmed among Japan, Europe and the USA. Maximum tolerated dose was determined to be 50 mg. Complete cytological response of cerebrospinal fluid (CSF) was obtained in a patient, and CSF cytological conversion of either ventricle or lumbar CSF from positive to negative was observed in four patients. Neurological improvements in 3 pts and no sign of worsening in one patient were observed, and grade IV toxicity based on National Cancer Institute-Common Toxicity Criteria was not encountered. In conclusion, NS-101 was effective for leptomeningeal carcinomatosis from solid tumors and the estimated maximum tolerated dose was 50 mg as approved in Europe and the USA.