Clinical and Pharmacological Study With 2B3-101 in Patients With Breast Cancer and Leptomeningeal Metastases

Leptomeningeal metastases (LM) develop when tumor cells reach the cerebrospinal fluid (CSF) and infiltrate the leptomeninges. Clinically symptomatic LM affects approximately 5 percent of patients with metastatic cancer. Among patients with LM caused by solid tumors, the most common tumor types are breast cancer (12-35%), lung cancer (10-26%), melanoma (5-25%) and gastrointestinal malignancies (4-14%). One to seven percent of LM patients have an unknown primary tumor.

The median survival of untreated patients with LM derived from solid tumors is only 6-8 weeks. Chemotherapy and radiotherapy of symptomatic central nervous system (CNS) sites extends the median survival up to 2-4 months. The median survival of patient with breast cancer and LM is even longer (4-6 months) with up to 25% long-term survivors. Many potentially highly efficacious intravenous chemotherapies are currently not effective to treat LM because they do not adequately cross the blood-CSF barrier. The effectiveness of intrathecal (IT) chemotherapy is thought to be limited due to rapid cerebrospinal fluid (CSF) clearance of the drug and/or insufficient penetration into larger (>1mm) tumor deposits in the subarachnoid space. Besides, only a few cytostatic drugs can be administered intrathecally because of neurotoxicity.

Doxorubicin, the anthracycline chemotherapeutic agent, has a well-established antineoplastic activity in breast cancer. It has triple action mechanisms, namely binding to the DNA strands by intercalation, blocking the enzyme topoisomerase II, necessary for DNA replication and formation of free radicals. The treatment of breast cancer patients with anthracycline-containing adjuvant chemotherapy reduces the relative risk (RR) of mortality in breast cancer patients with ± 38% per year in patients younger than 50 years and with ± 20% in patients between 50 and 69 years. [6] To optimally enhance the delivery of liposomal doxorubicin to the brain, to-BBB technologies B.V. has designed a glutathione (GSH) pegylated liposomal doxorubicin hydrochloride formulation (2B3-101). Coating of liposomes with PEG ensures the prolonged circulation time in plasma, whilst conjugation of GSH to the tips of the PEG molecules targets the liposomes towards the active GSH transporters on the BBB to enhance the delivery of doxorubicin to the brain.

In the ongoing Phase I/IIa study (M11TBB) the safety and preliminary efficacy of 2B3-101 is being determined in patients with brain metastases of solid tumours and patients with recurrent malignant glioma in 7 hospitals in The Netherlands, Belgium, France and USA.

This a feasibility study that aims to determine preliminary efficacy of treatment with 2B3-101 in patients with leptomeningeal metastases of breast cancer using the LM response score (see table 2).