In the melanoma brain metastases study arm of the expansion phase, each treatment cycle is 21 days long. Patients will receive a single IV dose of 2B3-101 at MTD determined for 2B3-101 as single agent in the dose escalation phase on day 1 of each cycle. In order to minimize the risk of infusion reactions 5% of the total dose (in mg) should be infused slowly over the first 30 minutes. As long as 2B3-101 is well tolerated, the remaining 95% of the infusion could thereafter be administered over the next 60 minutes, resulting in a total infusion time of 90 minutes. Blood samples will be taken on day 1, 2, 3, 5, 8 and 11 of cycle 1, day 1, 8 and 15 of cycle 2 and if applicable on day 1 of cycle 3 and on day 1 of cycle 4 to assess the PK profile during the first 4 cycles.