Improved therapeutic index by leucovorin of edatrexate, cyclophosphamide, and cisplatin regimen for non-small-cell lung cancer

Preemptive leucovorin administration minimizes pralatrexate toxicity without sacrificing efficacy

Balancing efficacy and safety of drugs is key for successful cancer therapy, as adverse reactions can prohibit the use of efficacious treatments. Pralatrexate (PDX) is a novel antifolate with a higher affinity for tumor cells than methotrexate, Food and Drug Administration (FDA) approved for use in relapsed and refractory peripheral T-cell lymphoma (PTCL) and transformed mycosis fungoides (T-MF). Patients with T-MF have a higher incidence of adverse events than patients with other lymphomas, necessitating a lower recommended dose of 15 mg/m(2) (vs. 30 mg/m(2) for PTCL). Dose-limiting toxicity (DLT) mucositis occurs in about 25% of patients with T-MF, but milder mucositis is observed in almost all patients with T-MF, frequently leading to therapy discontinuation despite clinical response. Leucovorin rescue is the standard of care for high-dose methotrexate therapy, but has not been studied or recommended for use with PDX. We report our clinical experience using leucovorin with PDX (30 mg/m(2)) with good clinical response and no DLTs. Prophylactic leucovorin deserves further investigation in prospective clinical trials to allow patients with cutaneous lymphomas to receive the full benefit of PDX therapy without intolerable toxicity.

The role of Pemetrexed (Alimta , LY231514) in lung cancer therapy

Pemetrexed (Alimta , LY231514) is a new multitargeted antifolate that inhibits several enzymes involved in the folate pathway. Pemetrexed is a potent inhibitor of thymidylate synthase, dihydrofolate reductase, and glycinamide ribonucleotide formyltransferase. Pemetrexed has demonstrated clinical activity in non-small-cell lung cancer (NSCLC) as well as in a broad array of other solid tumors including mesothelioma and breast, colorectal, bladder, cervical, gastric, and pancreatic cancer. In NSCLC, single-agent activity has been documented in the first- and second-line settings. Promising activity has also been demonstrated when pemetrexed is combined with cisplatin, vinorelbine, oxaliplatin, carboplatin, and gemcitabine. Low-level dietary supplement of folic acid and vitamin B12 has significantly improved the safety profile of pemetrexed without compromising its antitumor effect. In this review, the pharmacology and clinical activity of pemetrexed in NSCLC cancer is discussed.

Pharmacogenomic strategies for developing customized chemotherapy in non-small cell lung cancer

In this review, we deal with six groups of cytotoxic drugs commonly used in the treatment of non-small cell lung cancer (NSCLC). Although there are many reviews of thymidylate synthase (TS) and antifolate inhibitors, in this article, we have tried to highlight aspects that are more important for medical oncologists to consider when treating NSCLC patients. There is compelling evidence that TS gene transcripts and TS polymorphisms could be used to decide which patients can best benefit from adjuvant chemotherapy approaches, especially in colorectal cancer, and not less importantly, to tailor chemotherapy in metastatic NSCLC when using drugs akin to fluorouracil, such as pemetrexed. Secondly, cisplatin is central to chemotherapy combinations and evidence indicates that DNA repair capacity influences response to cisplatin-based regimens. ERCC1 gene transcript stands out as a predictive marker of cisplatin sensitivity. Thirdly, preliminary studies indicate that upregulation of beta-tubulin III correlates with response to paclitaxel and vinorelbine. Fourthly, overexpression of ribonucleotide reductase can influence response to gemcitabine. Fifthly, we describe mechanisms of resistance to topoisomerase I inhibitors, although this subject has not yet been completely elucidated. Finally, to understand the mechanisms of resistance to EGF-R inhibitors, which have been shown to be useful in many different types of cancer, the Src-STAT signaling pathways are described here in detail. Hopefully, the assessment of Src and of STAT-3 can be implemented as predictive markers.

Promising new agents in the treatment of non-small cell lung cancer

A number of new drugs and drug classes have recently become available for clinical testing which demonstrate significant antitumor activity in non-small cell lung cancer. The preclinical rationale, mechanism of action, toxicity profile and results of early trials of paclitaxel, docetaxel, edatrexate, CPT-11, topotecan, vinorelbine and gemcitabine in non-small cell lung cancer are reviewed.

New drugs in non-small cell lung cancer. An overview

Chemotherapy is rather ineffective in non-small cell lung cancer. However, in the last few years, a number of new anticancer agents have been developed which have definite activity in this disease. Among them are the taxanes and CPT-11, drugs with novel mechanisms of action, new antimetabolites (edatrexate and gemcitabine), and a new vinca alkaloid (vinorelbine). Furthermore, in the near future, the better understanding of lung cancer biology will help in devising new treatment strategies.

Schedule-dependent synergism of taxol or taxotere with edatrexate against human breast cancer cells in vitro

A new dihydrofolate reductase inhibitor, edatrexate (EDX), and the microtubule polymerization promotor, taxol (TXL) or taxotere (TXT), each have significant therapeutic activity against human breast cancer in clinical trials. Since they also have distinctly different mechanisms of actions and have mainly non-overlapping toxicities, they may be effective in combination in the treatment of this disorder. Schedule-dependent interactions between these taxanes and EDX against human breast adenocarcinoma cells (SK-Br-3) were quantitatively assessed in vitro to determine whether these interactions are synergistic or antagonistic. SK-Br-3 cells were grown as a monolayer in 96-well microplates. The dose-effect relationships of the drugs, singly and in combination, in inhibiting the growth over a 7-day period were determined by the SRB protein staining assays. Cell cultures were exposed to drug as a 3-h pulse at either 0-3 h or 24-27 h. Synergism or antagonism at different concentrations and at different effect levels were assessed with the median effect principle and the combination index-isobologram method using computer software. These methods were selected because they take into account both the potencies and the shape of the dose-effect curves. Exposure of cells to an equimolar combination of EDX + TXL (0-3 h) resulted in synergism at high effect levels. Pretreatment of cells with EDX (0-3 h) followed by TXL (24-27 h) showed even greater synergism in inhibiting cell growth. Moderate antagonism was observed with the reverse schedule. EDX + TXT (0-3 h) was additive, but pretreatment with EDX (0-3 hr) followed by TXT (24-27 h) showed synergism. However, the reverse order showed antagonism. Studies on another breast tumor cell line, ZR-57-1, also showed the schedule of EDX (0-3 h) + TXT or TXL (24-27 h) to be more synergistic than, the other two schedules examined. These results show potent schedule-dependent synergism of the combinations of TXL or TXT with EDX, and should form a rationale for designing clinical protocols utilizing these agents particularly for the treatment of breast cancer patients.

Leucovorin rescue of human cancer and bone marrow cells following edatrexate or methotrexate

We have examined the cytotoxic activities of edatrexate (EDX) and methotrexate (MTX) and their reversal by leucovorin in nine human cancer cell lines and in human bone marrow CFU-GM cells. EDX was 3.7- to 123-fold more toxic than MTX against the cancer cell lines and 25-fold against the bone marrow cells. Lower EDX concentrates generally were needed to inhibit cancer cell growth relative to bone marrow cells, however, whereas bone marrow and cancer cell growth were more often susceptible to the same MTX concentrations. The new antifolate was metabolized to long-chain polyglutamates to a greater extent than MTX in seven cell lines. Leucovorin at 0.2 microM rescued two breast cancer and two non-small cell lung cancer cell lines to a lesser extent following EDX than MTX, but significant rescue was observed in two head and neck cancer cell lines that formed large amounts of polyglutamates. These cell lines also accumulated reduced folates to a greater extent than the other cell lines following leucovorin exposure. Leucovorin rescued bone marrow cells following MTX but only partially following the highest EDX concentrations. EDX may enjoy a better therapeutic index than MTX against some cancer cell lines relative to bone marrow precursor cells, especially after leucovorin rescue.

Effective combination therapy of metastatic murine solid tumors with edatrexate and the vinca alkaloids, vinblastine, navelbine and vindesine

Studies are described in which a new folate analogue, edatrexate (EDX), in combination with the vinca alkaloids, vinblastine (VBL), navelbine (NVB) or vindesine (DVA) was evaluated against E0771 mammary adenocarcinoma, T241 fibrosarcoma and the Lewis lung tumor. Each of the four agents when given individually to animals 3 days after transplant of these tumors resulted in increases in survival of 53-143%. The relative effectiveness of these agents was (in increasing order) VBL, NVB congruent to DVA, EDX, with no long-term survivors obtained with any. Combination therapy with EDX and vinca alkaloids required dosage attenuation but was still markedly more effective. Treatment of E0771 and T241 tumors with EDX and either NVB or DVA increased survival 3- to 4-fold compared with therapy with individual agents and yielded 40-70% long-term survivors, while EDX with VBL increased survival 2- to 3-fold and yielded 20-40% long-term survivors. Simultaneous or sequential (EDX given 24 h before vinca alkaloid) administration of combined therapy was equally effective. Sequential administration of these agents at the same doses in the reverse order was highly toxic and required further dosage attenuation which compromised efficacy. Effects of these combinations against the Lewis Lung tumor were not as pronounced and were somewhat schedule-dependent. Simultaneous administration of EDX with VBL, NVB or DVA increased survival 2- to 3-fold over that obtained with single agents alone and yielded 10-40% long-term survivors, while sequential administration increased survival < 2-fold over that obtained with single agents and yielded 0-20% long-term survivors. These results suggest that combined therapy with these agents in patients may have appreciable utility and provide a basis for further clinical trials.