Novel antineoplastics targeting genetic changes in colorectal cancer

Cytotoxic chemotherapy remains the mainstay of the medical -management of colorectal cancer (CRC). Research over the last two decades has led to a molecular understanding of the oncogenic mechanisms involved in CRC and has contributed to the rational development of antineoplastics that target these mechanisms. During carcinogenesis, genetic changes often occur in molecules that play key functional roles in cancer such as cell proliferation, angiogenesis, apoptosis, cell death and immune-mediated destruction of cancer cells. Here, we review novel antineoplastics that are approved or in development for CRC that target molecules associated with genetic aberrations in CRC. Some of these targeted antineoplastics have proven effective against other solid tumors and hold promise in treating CRC whereas others are now routinely used in combination with cytotoxic agents. This article reviews antineoplastics that target genetic changes in CRC, their antitumor mechanisms, and their stage of development.

Decreased exposure to sunitinib due to concomitant administration of ifosfamide: results of a phase I and pharmacokinetic study on the combination of sunitinib and ifosfamide in patients with advanced solid malignancies

BACKGROUND

This study aimed to define the maximally tolerated dose (MTD) of sunitinib combined with two different infusion schedules of ifosfamide.

METHODS

Patients with advanced solid tumours, good performance score, good organ function, and no standard therapy available were eligible. Continuous once daily sunitinib, in escalating doses per cohort, was combined with ifosfamide, 9 g m(-2) for 3 days or 6 g m(-2) for 5 days, administered every 3 weeks. Pharmacokinetic (PK) and pharmacodynamic (PD) assessments were performed.

RESULTS

With growth-factor support, the MTD of sunitinib combined with either ifosfamide schedule was 12.5 mg in 32 patients enrolled. Neutropenia-related adverse events were dose-limiting toxicities. Sunitinib did not affect ifosfamide PK. Ifosfamide significantly decreased exposure to sunitinib and increased exposure to its metabolite, SU12662. No consistent changes in PD parameters were observed.

CONCLUSION

With growth-factor support, the MTD of sunitinib with both ifosfamide schedules was 12.5 mg. Ifosfamide produced decreased sunitinib blood levels because of CYP3A induction. As PK interactions cannot explain the relatively low sunitinib doses that can be combined with ifosfamide, synergy in toxicity is likely. Whether this also holds true for anti-tumour activity needs to be further explored.

Sunitinib in solid tumors

BACKGROUND

Until recently, few treatments were available for renal cell carcinoma (RCC) and gastrointestinal stromal tumors (GIST). Several targeted agents inhibiting key pathogenetic pathways have since been developed for RCC (sunitinib, sorafenib, bevacizumab, temsirolimus, everolimus) and GIST (imatinib, sunitinib). Sunitinib is a multi-kinase inhibitor of VEGFR-2, PDGFR (alpha,beta), FLT-3, KIT, CSF-1 and RET.

OBJECTIVE

To summarize the literature regarding the structure, pharmacokinetics, pharmacodynamics, toxicity and current clinical use of sunitinib. Other potential roles for this drug in RCC, GIST and other tumor types will be discussed.

METHODS

A literature search identified relevant (pre)clinical studies of sunitinib and other relevant agents.

RESULTS/CONCLUSIONS

Sunitinib revolutionized the management of advanced RCC and GIST. With the realization that cross-resistance between targeted agents is incomplete, evolving strategies include sequential treatment, concurrent treatment, and biomarker development. Sunitinib also shows promise in several other tumor types that lack therapeutic options. What remains less clear is its role in tumors that are not heavily dependent on a central pathogenetic pathway, especially if effective cytotoxic therapies exist. Future clinical trials will clarify whether there is a role for sunitinib in these tumors, possibly in combination with cytotoxic agents.