A randomized phase II trial of pemetrexed plus irinotecan (ALIRI) versus leucovorin-modulated 5-FU plus irinotecan (FOLFIRI) in first-line treatment of locally advanced or metastatic colorectal cancer

Prolonged Pemetrexed Infusion Plus Gemcitabine in Refractory Metastatic Colorectal Cancer: Preclinical Rationale and Phase II Study Results

LESSONS LEARNED

Difficulties in translating in vitro results into clinical practice are inevitable.Further efforts to verify the efficacy of alternative schedules of pemetrexed in solid tumors are encouraged.

BACKGROUND

We investigated the cytotoxic activity of pemetrexed in combination with several drugs (gemcitabine, carboplatin, vinorelbine, and mitomycin C) using different exposure schedules in three colon cancer cell lines. The best results were obtained with the following schedule: a prolonged pemetrexed exposure followed by a 48-hour wash-out and then gemcitabine. This combination was then advanced to a phase II clinical trial.

METHODS

Patients with metastatic colorectal cancer in progression after standard treatment were included in the study. Adequate bone marrow reserve, normal hepatic and renal function, and an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2 were required. Treatment consisted of an 8-hour intravenous infusion of pemetrexed 150 mg/m² on day 1 and a 30-minute intravenous infusion of gemcitabine 1,000 mg/m² on day 3 of each cycle, repeated every 14 days.

RESULTS

Fourteen patients were enrolled onto the study (first step). No objective responses were seen, and evidence of stable disease was observed in only one of the 12 evaluable patients. The most important grade 3-4 side effects were hematological toxicity (neutropenia 64.2%, thrombocytopenia 71.4%, anemia 28.7%), fatigue (50.0%), and stomatitis (21.5%). Median overall survival and time to progression were 5.8 months (95% confidence interval [CI]: 3.9-7.1) and 2.1 months (95% CI: 1.7-2.8), respectively.

CONCLUSION

The experimental pemetrexed-gemcitabine combination proved to be inactive and moderately toxic.

Reduced folate and serum vitamin metabolites in patients with rectal carcinoma: an open-label feasibility study of pemetrexed with folic acid and vitamin B12 supplementation

The objectives of this single-center, open-label, phase II study were to evaluate (a) the feasibility and safety of neoadjuvant administration of pemetrexed with oral folic acid and vitamin B₁₂ (FA/B₁₂) in newly diagnosed patients with resectable rectal cancer and (b) intracellular and systemic vitamin metabolism. Patients were treated with three cycles of pemetrexed (500 mg/m², every 3 weeks) and FA/B₁₂ before surgery. The reduced folates tetrahydrofolate, 5-methyltetrahydrofolate, and 5,10-methylenetetrahydrofolate were evaluated from biopsies in tumor tissue and in adjacent mucosa. Serum levels of homocysteine, cystathionine, and methylmalonic acid were also measured. All 37 patients received three cycles of pemetrexed; 89.2% completed their planned dosage within a 9-week feasibility time frame. Neither dose reductions nor study drug-related serious adverse events were reported. Reduced folate levels were significantly higher in tumor tissue compared with adjacent mucosa at baseline. After FA/B₁₂ administration, tissue levels of reduced folates increased significantly and remained high during treatment in both tumor and mucosa until surgery. Serum levels of cystathionine increased significantly compared with baseline after FA/B₁₂ administration, but then decreased, fluctuating cyclically during pemetrexed therapy. Homocysteine and methylmalonic acid levels decreased significantly after FA/B₁₂ administration, and remained below baseline levels during the study. These results indicate that administration of three neoadjuvant cycles of single-agent pemetrexed, every 3 weeks, with FA/B₁₂ in patients with resectable rectal cancer is feasible and tolerable. Tissue and serum vitamin metabolism results demonstrate the influence of pemetrexed and FA/B₁₂ on vitamin metabolism and warrant further study.

Phase 1 dose de-escalation trial of the endogenous folate [6R]-5,10-methylene tetrahydrofolate in combination with fixed-dose pemetrexed as neoadjuvant therapy in patients with resectable rectal cancer

Background Modufolin® ([6R]-5,10-methylene tetrahydrofolate; [6R]-MTHF) is an endogenous biomodulator that is being developed as an alternative to leucovorin, a folate prodrug used in the treatment of colorectal cancer. The objective of this phase 1 dose de-escalation trial was to estimate the minimum tolerated dose of [6R]-MTHF to be used in combination with pemetrexed 500 mg/m² in the neoadjuvant treatment of patients with rectal cancer. Methods Adult patients (≥18 years) with resectable rectal adenocarcinoma were allocated to [6R]-MTHF doses of 500, 100, 50, and 10 mg/m² in combination with pemetrexed 500 mg/m². [6R]-MTHF was administered as an intravenous (i.v.) bolus injection 1 week prior to the first dose of pemetrexed and then once weekly for 9 weeks; pemetrexed was administered by i.v. infusion once every 21 days for three cycles. Results Twenty-four patients (mean [SD] age, 63.1 [12.9] years) were enrolled in the study. A total of 72 treatment-related adverse events (AEs) were reported, of which the most common were fatigue (n = 17; 23.6 %), nausea (n = 10; 13.9 %), and diarrhea (n = 5; 6.9 %). The incidence of treatment-related AEs by [6R]-MTHF dose level (500, 100, 50, 10 mg/m²) was 11.1 % (n = 8), 13.9 % (n = 10), 45.8 % (n = 33), and 29.2 % (n = 21), respectively. There were no dose-limiting toxicities, and only two (2.8 %) treatment-related AEs were grade 3 in severity. Of the 11 serious AEs reported, none were considered to be related to [6R]-MTHF treatment. Conclusions The results of this phase 1 study indicate that the estimated minimum tolerated dose of [6R]-MTHF was 100 mg/m² once weekly in combination with pemetrexed 500 mg/m². The low toxicity profile of [6R]-MTHF supports its further evaluation as a component of systemic chemotherapy in the management of colon and rectal cancer.

Effects of pemetrexed, gefitinib, and their combination on human colorectal cancer cells

PURPOSE

The study investigated the effects of pemetrexed, gefitinib, and their combination on human colorectal cancer cells.

METHODS

Six human colorectal cancer cells were exposed to pemetrexed, gefitinib, and their combination. Antitumor effects were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Thymidylate synthase (TS) mRNA expression and EGFR mutation were studied by real-time RT-PCR and DNA sequence determination. Pharmacological interaction was studied using the combination index method. Cell cycle distribution and apoptosis were determined by flow cytometry. Activity assay was performed to assess the effects of drugs on TS activity, and Western blot was performed to assess the protein expression of pEGFR, pAKT, and pERK 1/2.

RESULTS

Six colorectal cancer cells are all sensitive to pemetrexed, and TS gene expression of cells was negatively related to pemetrexed sensitivity. The cytotoxic synergism was observed in concurrent pemetrexed combined with gefitinib and sequential pemetrexed followed by gefitinib. The combination of pemetrexed and gefitinib modulated cell cycle and induced apoptosis. Pemetrexed combined with gefitinib decreased TS mRNA expression and in situ activity. Pemetrexed induced an EGFR-mediated activation of the phosphatidylinositol 3-kinase/AKT and ERK pathway, which was inhibited by gefitinib.

CONCLUSIONS

Pemetrexed is a promising agent, and pemetrexed combined with gefitinib has a significantly synergistic effect on colorectal cancer cells, which seems to present a strategy of pemetrexed combined with EGFR-TKIs in colorectal cancer treatment.

Effect of folic acid and vitamin B12 on pemetrexed antifolate chemotherapy in nutrient lung cancer cells

Pemetrexed (MTA) is a multitargeted antifolate drug approved for lung cancer therapy. Clinically, supplementation with high doses of folic acid (FA) and vitamin B₁₂ (VB12) lowers MTA cytotoxicities. An antagonistic effect of FA/VB12 on MTA efficacy has been proposed. However, patients who receive FA/VB12 show better tolerance to MTA with improved survival. The aims of this study are to investigate the modulation of FA and VB12 on MTA drug efficacy in human nonsmall cell lung cancer (NSCLC) cell lines. The sensitivities of cells, apoptosis, and MTA-regulated proteins were characterized to determine the possible effects of high doses of FA and VB12 on MTA efficacy. MTA has the lowest efficacy under 10% serum conditions. However, supplementation with FA and VB12 individually and additively reversed the insensitivity of NSCLC cells to MTA treatment with 10% serum. The enhanced sensitivities of cells following FA/VB12 treatment were correlated with increasing apoptosis and were specific to MTA but not to 5-fluorouracil (5-FU). Enhanced sensitivity was also associated with p21^WAF1/Cip1 expression level. Our results revealed no antagonistic effect of high doses of FA/VB12 on MTA efficacy in cancer cells grown in nutrient medium. Furthermore, these data may partially explain why supplementation of FA and VB12 resulted in better survival in MTA-treated patients.

Meta-analysis of the association between progression-free survival and overall survival in metastatic colorectal cancer

PURPOSE

The validity of progression-free survival (PFS) as a surrogate endpoint for overall survival (OS) in metastatic colorectal cancer (mCRC) trials has been studied, primarily in first-line treatment. The relationship between PFS and OS has not been well studied in later lines of treatment.

METHODS

We conducted a systematic literature review of mCRC phase 2 and 3 clinical trials that reported OS and PFS (or time-to-progression [TTP]) data. Correlation between endpoints (either PFS alone or PFS aggregated with TTP [PFS_TTP]) was estimated within treatment arms. Treatment effect was the ratio of the median time to OS, PFS, or PFS_TTP in the "control" versus "experimental" arm. We conducted meta-regression analyses and performed receiver-operating characteristic (ROC) analysis.

RESULTS

We analyzed data from 62 articles (23,527 patients). A high positive correlation was found between median PFS_TTP and median OS within treatment arms (r = 0.87; 95% confidence interval [CI], 0.82-0.91) and also between the median OS and median PFS (r = 0.89, 95% CI, 0.83-0.93)]. R(2) was 0.48 for PFS_TTP and 0.59 for PFS; R (2) for PFS_TTP was higher for first-line (R(2) = 0.54) than second-line studies (R(2) = 0.38). The ROC analysis is presented as a conceptual tool for evaluating the performance of PFS as a surrogate for OS at various thresholds.

CONCLUSIONS

The correlation of PFS, alone or aggregated with TTP, with OS in clinical trials of patients with mCRC is robust across lines of therapy and provides a useful means of predicting improvements in OS using PFS data.

CoFactor: Folate Requirement for Optimization of 5-Fluouracil Activity in Anticancer Chemotherapy

Intracellular reduced folate exists as a "pool" of more than 6 interconvertable forms. One of these forms, 5,10 methylenetetrahydrofolic acid (CH(2)THF), is the key one-carbon donor and reduced folate substrate for thymidylate synthase (TS). This pathway has been an important target for chemotherapy as it provides one of the necessary nucleotide substrates for DNA synthesis. The fluoropyrimidine 5-fluorouracil (5-FU) exerts its main cytotoxic activity through TS inhibition. Leucovorin (5-formyltetrahydrofolate; LV) has been used to increase the intracellular reduced folate pools and enhance TS inhibition. However, it must be metabolized within the cell through multiple intracellular enzymatic steps to form CH2THF. CoFactor (USAN fotrexorin calcium, (dl)-5,10,-methylenepteroyl-monoglutamate calcium salt) is a reduced folate that potentiates 5-FU cytotoxicity. According to early clinical trials, when 5-FU is modulated by CoFactor instead of LV, there is greater anti-tumor activity and less toxicity. This review presents the emerging role of CoFactor in colorectal and nongastrointestinal malignancies.

Phase II Study of Biweekly Pemetrexed Plus Irinotecan as Second-Line Therapy for Metastatic Colorectal Cancer

Background. This open-label, single-arm, two-stage, Phase II study investigated the efficacy and safety of bi-weekly pemetrexed combined with irinotecan, in patients with metastatic colorectal cancer (mCRC), after first-line chemotherapy using FOLFOX regimen. Patients and methods. Patients received pemetrexed 400 mg/m² as a 10-minute intravenous infusion (with vitamin supplementation) followed by irinotecan 180 mg/m² as a 90-minute infusion on day 1 of a 14-day cycle, for a maximum of 12 cycles. The primary endpoint was response rate (RR; H₀ ≤ 5%, H_a ≥ 20%, α = 0.05, power = 90%). Secondary endpoints were duration of response, progression-free survival (PFS), overall survival (OS), and toxicities. Results. Partial response was observed in six out of 44 patients enrolled in the study (RR = 13.6%). The median PFS and OS were 4.0 and 13.9 months, respectively. The most common grade 3-4 toxicities were fatigue: 20.5% of patients, neutropenia: 18.6%, diarrhea: 13.6%, elevated transaminases: 9.5%, anemia: 9.3%, and vomiting: 6.8%. Conclusion. Pemetrexed plus irinotecan administered every two weeks is an active and well-tolerated regimen in mCRC patients pretreated with FOLFOX regimen. However, this regimen does not seem to provide clinically relevant advantage over historical data of a classical FOLFIRI regimen.