cis-Bis-neodecanoato-trans-R,R-1,2-diaminocyclohexaneplatinum++ +(II) (NDDP) is a liposome dependent cisplatin analogue since the liposome carrier is required for its i.v. administration and for its biological activity. A Phase I study of liposome entrapped NDDP (L-NDDP) was performed using a single i.v. injection every 4 weeks. L-NDDP was prepared and characterized at M. D. Anderson Cancer Center. The maximum tolerated dose of L-NDDP was 312.5 mg/m2. The dose-limiting toxicity was myelosuppression, affecting all three blood cell lineages. The granulocyte nadir occurred on days 14-18, and the platelet nadir consistently earlier (days 11-12). The median day of recovery of blood cell counts was day 21 (range, 18-32). Other toxicities included grade 2 nausea and vomiting, fever consisting of a single temperature spike in most patients, grade 1 diarrhea after 60% of courses, and grade 1-2 malaise lasting for 5-10 days after the infusion in 73% of courses. Transient alanine aminotransferase elevations without clinical relevance were common. No signs of renal dysfunction or ototoxicity were observed. One patient with a preexisting peripheral neuropathy showed some progression of the neuropathy after a cumulative dose of 1605 mg/m2. Except for fever and transient liver dysfunction, no liposome related side effects were observed in spite of the high doses of lipid administered. The blood clearance of L-NDDP fits a two-compartment model at lower doses and a single-compartment model at the maximum tolerated dose, suggesting that saturation of the reticuloendothelial organs occurs at the maximum tolerated dose. Two minimal responses were observed. L-NDDP has a toxicity profile similar to that of carboplatin. Phase II studies to address the issue of how the therapeutic index of platinum compounds is affected by liposome entrapment are being planned.