Pharmacokinetics, Safety, and Efficacy of a Liposome Encapsulated Thymidylate Synthase Inhibitor, OSI-7904L [(S)-2-[5-[(1,2-Dihydro-3-methyl-1-oxobenzo[f]quinazolin-9-yl)methyl]amino-1-oxo-2-isoindolynl]-glutaric Acid] in Mice

Opportunities and challenges in commercial pharmaceutical liposome applications

In the 1980s, the center of entrepreneurial activity for the application of liposome science to medicine took the form of a company called Vestar Inc. (which became NeXstar Pharmaceuticals Inc., and eventually a division of Gilead Sciences, with merger and acquisition activity). This company was formed from science initially developed at the California Institute of Technology and the City of Hope, and involving several other local academic and treatment centers. This company eventually produced two commercial liposomal therapeutics, and created a particular paradigm of formulation goals, formulation development, characterization, and production unique among the set of companies that emerged around the same time. A number of clinical candidates were also developed, but failed to achieve commercialization. Nevertheless, several of these provide still relevant lessons and guidance for the field. Key adaptations of this technology to lower cost applications have also been carried out and are examined.

A phase I and pharmacokinetic study of OSI-7904L, a liposomal thymidylate synthase inhibitor in combination with oxaliplatin in patients with advanced colorectal cancer

PURPOSE

OSI-7904L is a liposomal formulation of a potent thymidylate synthase (TS) inhibitor. This phase I study evaluated the safety, tolerability and pharmacokinetics (PK) of OSI-7904L administered in combination with oxaliplatin every 21 days in patients with advanced colorectal carcinoma.

METHOD

A 3+3 study design was utilized at predefined dose levels. Polymorphisms in the TS enhancer region and XPD enzyme were investigated as potential predictors of efficacy and toxicity.

RESULTS

Fourteen patients received 76 cycles of treatment. At the highest dose level (OSI-7904L 9 mg/m(2), oxaliplatin 130 mg/m(2)) investigated, one of nine patients experienced dose-limiting toxicity of grade 3 oral mucositis with cycle 1 and five further patients required dose reductions. The toxicity profile of stomatitis, diarrhea, nausea, fatigue, sensory neuropathy and skin rash was consistent with that expected for a TS inhibitor/oxaliplatin combination regimen. PK analysis showed high interpatient variability with no detectable interaction between OSI-7904L and oxaliplatin. Partial radiological responses were documented in two patients.

CONCLUSIONS

The recommended regimen for further investigation is OSI-7904L 9 mg/m(2) and oxaliplatin 130 mg/m(2).

A randomised phase II study of OSI-7904L versus 5-fluorouracil (FU)/leucovorin (LV) as first-line treatment in patients with advanced biliary cancers

The prognosis of advanced biliary tract carcinoma is poor with chemotherapy limited to a palliative role. This randomised study was designed to evaluate the effectiveness of a new liposomal thymidylate synthase inhibitor (TSI), OSI-7904L, in parallel with a modified de Gramont regimen of 5-FU/LV in patients with advanced biliary cancer. Patients with previously untreated advanced or metastatic carcinoma of the biliary tract were randomised to receive either OSI-7904L 12 mg/m2 intravenously every 21 days or a modified de Gramont schedule of 5-FU/LV (intravenous l-LV 200 mg/m2, bolus 5-FU 400 mg/m2 and a 46-h infusion of 5-FU 2,400 mg/m2) every 14 days. Twenty-two patients were randomised, 11 to each group. No patients responded in the OSI-7904L arm, while one patient achieved a partial response in the 5-FU/LV arm. The rates of disease stabilisation were 4/11 (OSI-7904L) and 10/11 (5-FU/LV). Both treatment arms were generally well tolerated. These results show that the activity of OSI-7904L is below a level of clinical relevance in advanced biliary tract cancer, providing only a small degree of disease stabilisation. A simplified de Gramont schedule appears to have marginally more activity. Both treatments were well tolerated.

Novel Therapeutic Developments Other Than EGFR and VEGF Inhibition in Colorectal Cancer

Developments that may improve existing cytotoxic therapy for colorectal cancer (CRC) include alternatives to 5-fluorouracil (5-FU) such as the liposomal Thymidylate Synthase inhibitor OSI-7904L and the multitargeted antifolate pemetrexed. Studies have explored means of reformulating irinotecan, modulating its pharmacokinetics, and enhancing its activity by maximizing DNA damage through poly(ADP-ribose) polymerase inhibition. Cell cycle inhibitors may offer an alternative to combination with 5-FU. However, as standard regimens become more complex, so do the clinical trials needed to develop new agents, and the path to registration becomes ever more tortuous. It is therefore likely that several drugs with promise in CRC will not be developed for this indication.

Multicentre phase II pharmacokinetic and pharmacodynamic study of OSI-7904L in previously untreated patients with advanced gastric or gastroesophageal junction adenocarcinoma

A two-stage Simon design was used to evaluate the response rate of OSI-7904L, a liposome encapsulated thymidylate synthase inhibitor, in advanced gastric and/or gastroesophageal adenocarcinoma (A-G/GEJA), administered intravenously at 12 mg m(-2) over 30 min every 21 days. Fifty patients were treated. Median age was 64 years (range 35-82), 62% were male and 89% had ECOG PS of 0/1. A total of 252 cycles were administered; median of 4 per patient (range 1-21). Twelve patients required dose reductions, mainly for skin toxicity. Investigator assessed response rate was 17.4% (95% CI 7.8-31.4) with one complete and seven partial responses in 46 evaluable patients. Twenty-one patients (42%) had stable disease. Median time to progression and survival were 12.4 and 36.9 weeks, respectively. NCI CTCAE Grade 3/4 neutropenia (14%) and thrombocytopenia (4%) were uncommon. The main G3/4 nonhaematological toxicities were skin-related 22%, stomatitis 14%, fatigue/lethargy 10%, and diarrhea 8%. Pharmacokinetic data showed high interpatient variability. Patients with higher AUC were more likely to experience G3/4 toxicity during cycle 1 while baseline homocysteine did not predict toxicity. Response did not correlate with AUC. Elevations in 2'-dU were observed indicating target inhibition. Analysis of TS genotype, TS protein and expression did not reveal any correlation with outcome. OSI-7904L has activity in A-G/GEJA similar to other active agents and an acceptable safety profile.

Phase I Study of OSI-7904L, a Novel Liposomal Thymidylate Synthase Inhibitor in Patients with Refractory Solid Tumors

PURPOSE

OSI-7904L is a liposomal formulation of a potent noncompetitive thymidylate synthase inhibitor (TSI) that does not require polyglutamation for activity. This phase I study was done to establish the safety, tolerability, maximum tolerated dose, recommended dose, and pharmacokinetics of OSI-7904L in patients with advanced solid tumors refractory to standard therapy.

DESIGN

OSI-7904L was given as a 30-minute i.v. infusion every 21 days to 31 patients at eight dose levels from 0.4 to 15.0 mg/m(2), using three patients per dose level, up to 10 patients at the recommended dose. Baseline plasma homocysteine and 2'-deoxyuridine and genotype polymorphism were measured as potential predictors of biological activity.

RESULTS

Minimal toxicity was reported up to 9.6 mg/m(2), but dose-limiting toxicity was seen in both patients at 15 mg/m(2) including stomatitis, fatigue, tachyarrhythmia, rash and hand-foot syndrome, diarrhea, and fatal neutropenic sepsis. Other toxicity such as nausea and vomiting was mild or moderate. This resulted in the investigation of an intermediate dose level of 12 mg/m(2), identified as the recommended dose for phase II studies. Prolonged disease stabilization was reported in 11 of 31 heavily pretreated patients. Pharmacokinetic data indicate that this liposomal formulation alters the disposition properties of the parent drug resulting in a prolonged plasma residence time.

CONCLUSIONS

OSI-7904L given as a 30-minute i.v. infusion every 21 days is feasible and well tolerated at the recommended phase II dose of 12 mg/m(2). The main toxicities are rash, pruritus, lethargy, stomatitis, and myelosuppression. Observed toxicities were predictable and characteristic for TSIs.

Low folate conditions may enhance the interaction of trifluorothymidine with antifolates in colon cancer cells

PURPOSE

Trifluorothymidine (TFT) is a fluoropyrimidine that is part of the novel combination metabolite TAS-102, in which TFT is combined with a potent thymidine phosphorylase inhibitor (TPI). TAS-102 is currently tested as an orally chemotherapeutic agent in different schedules in a phase I study. In its monophosphate form, TFT can inhibit thymidylate synthase (TS) activity after binding to the TS-nucleotide binding site leading to dTTP depletion, and in its triphosphate form TFT is incorporated into DNA, eventually leading to DNA damage. In this in vitro study, we investigated whether TFT could potentiate cytotoxicity of the antifolate-based TS inhibitors AG337 (Nolatrexed), ZD1694 (Raltitrexed) and GW1843; and whether increased TS inhibition or DNA damage would be related to this result.

METHODS

The drug combinations were studied in colon cancer cell lines either grown at low or high folate conditions. Multiple drug effect analysis was performed after measuring growth inhibition when the drugs were combined (MTT Assay) and expressed as Combination Index (CI), where CI<0.9 indicates synergism, CI=0.9-1.1 indicates additivity and CI>1.1 indicates antagonism. Drug target analysis was performed using the TS in situ inhibition assay and the FADU DNA-damage assay. Cells were exposed to either the drugs alone or in combination to determine the effect on TS activity and DNA damage induction, respectively.

RESULTS

Three experimental procedures were used to test the interaction of the drugs: either one of the drugs was kept at a constant concentration (IC25) or two drugs were added in a 1:1 IC50-based molar ratio. The combinations of TFT with one of the antifolates in which one of the drugs was kept at a constant concentration were synergistic for all antifolates in WiDr/F cells, which grow in low folate medium (CI=0.6-0.8), but only additive to antagonistic for the cell lines growing in high folate medium: TFT-AG337: CI=0.9-2.3; TFT-ZD1694: CI=0.9-1.3; TFT-GW1843: CI=0.8-1.7. The procedure in which the two drugs were added in a 1:1 IC50-based molar ratio showed antagonism for all three combinations in all cell lines (CI>2.7). TS inhibition (14.3%) and DNA damage (8%) were more pronounced than expected (P<0.05) when TFT was combined with GW1843 in WiDr/F cells, in contrast to AG337 and ZD1694, which showed inhibiting effects as expected (additive).

CONCLUSIONS

The combination of TFT with the antifolates AG337, ZD1694 and GW1843 is mainly additive when the drugs are given simultaneously and this is mediated by an additive TS inhibition and DNA damage. The drug interaction may partly be dependent on the folate homeostasis since WiDr/F cells growing at low folate conditions show pronounced synergism in growth inhibition, two-sided TS inhibition and DNA damage, especially when TFT is combined with the tight-binding TS inhibitor GW1843.