Immunoglobulin G fragment C receptor polymorphisms and response to trastuzumab-based treatment in patients with HER-2/neu-positive metastatic breast cancer

13090

Background: A potential mechanism of action of the humanized anti-HER-2/neu monoclonal antibody Trastuzumab involves antibody-dependent cellular cytotoxicity (ADCC) with the activation of immune effector cells via their immunoglobulin G fragment C receptors (FcγRs). Trastuzumab has been shown to engage both activation (FcγRIIIa; FcγRIIa) and inhibitory (FcγRIIb) antibody receptors on myeloid cells and several FcγR polymorphisms have been identified that may affect the antibody-dependent cytotoxicity of natural killer cells and macrophages. Methods: Forty consecutive HER-2/neu-positive (FISH+) metastatic breast cancer patients receiving a trastuzumab-based treatment (combined with paclitaxel for the majority) were examined for the FcγRIIIa 158 valine (V)/phenylalanine (F), FcγRIIa 131 histidine (H)/arginine (R), and FcγRIIb 232 isoleucine (I)/threonine (T) polymorphisms. A PCR-RFLP based assay using genomic DNA was performed for FcγRIIIa and FcγRIIa genotyping, while PCR-SSCP methods using complementary DNA were utilized for FcγRIIb. Patients’ peripheral blood mononuclear cells were drawn before treatment initiation and their trastuzumab-mediated killing function was measured by 51Cr release using a HER-2/neu-expressing human breast cancer cell line as a target. The results were then correlated with clinical outcome of these patients. Results: Median age was 60 years (range 26–83 years). Thirty-six (90%) patients received a trastuzumab-based treatment as first-line therapy. The overall clinical benefit rate (CR+PR+SD) was 65% (95% Confidence Interval: 62–71%), including 8 (20%) complete and 11 (27.5%) partial responses. Median survival was 22.3 mo with a median PFS of 7 mo. Trastuzumab-based treatment was well tolerated and no changes in cardiac function were observed. Conclusions: This study evaluates for the first time the potential role of FcγR polymorphisms in predicting response to trastuzumab-based treatment. Results according to this study purpose will be presented at the meeting.

No significant financial relationships to disclose.

IDN 5390: an oral taxane candidate for protracted treatment schedules

The recognition of the antiangiogenic properties of taxanes provides a basis for novel therapeutic approaches. A prolonged exposure to low drug concentrations has been proposed to be the most suitable approach to exploit the antiangiogenic potential of cytotoxic agents. Such schedule is required to target preferentially slowly dividing endothelial cells. The protracted use of taxanes could benefit from the availability of a taxane endowed with a favourable tolerability profile. Among compounds of a novel series of C-seco taxanes, IDN 5390 was originally selected on the basis of its potent antimotility activity and poor cytotoxicity on endothelial cells. The aim of the study was to investigate the preclinical pharmacologic profile of IDN 5390 in a variety of human tumour xenografts, including ovarian and colon carcinoma and a glioblastoma. IDN 5390, delivered by s.c. injection, daily for 5 days per week, exhibited a high activity against all tumours investigated (tumour growth inhibition was always >85%) in the range of well-tolerated doses. The maximum tolerated dose/injection (MTD), with no signs of systemic or local vesicant toxicity, was 120 mg kg(-1). In contrast, paclitaxel, delivered according to the same schedule, exhibited a variable antitumour efficacy associated with a substantial local toxicity (MTD=10 mg kg(-1)). Considering the remarkable efficacy of IDN 5390 delivered s.c. by protracted treatment schedule, the oral route of administration was further investigated, as the most suitable for daily treatment. Indeed, a good bioavailability of oral IDN 5390 was found. Oral IDN 5390 maintained a substantial efficacy against human tumour xenografts, including paclitaxel-resistant tumours, without loss of potency with respect to s.c. administration. In conclusion, the therapeutic advantages of IDN 5390, over paclitaxel, in protracted daily treatment schedules are represented by the oral efficacy and the high tolerability, which are favourable features to exploit the antiangiogenic potential and to design combinations with other effective agents.

A novel taxane active against an orthotopically growing human glioma xenograft

BACKGROUND

The development of effective chemotherapy for central nervous system tumors is hampered by the blood-brain barrier and by limited drug diffusion in the brain tissue. BAY 59-8862 is a new taxane analog that was selected and developed for its activity against tumors with a P-glycoprotein-mediated, multidrug-resistant phenotype. Because P-glycoprotein is implicated in limiting the access of drugs to central nervous system tumor targets, the objective of this study was to evaluate the ability of intravenously administered BAY 59-8862 to affect the growth of central nervous system tumors.

METHODS

The U-87 MG human glioma cell line was xenografted orthotopically (intracranially) in nude mice. Paclitaxel or BAY 59-8862 was delivered intravenously four times every fourth day, and antitumor efficacy was assessed by examining the effects on mouse survival time and by histologic examination of mouse brain. Drug levels in plasma and brain were determined according to a high-performance liquid chromatography method.

RESULTS

The analog was as potent as paclitaxel in inhibiting the proliferation of three human glioma cell lines (U-87 MG, SW1783, and GBM) and was as effective as paclitaxel in inhibiting the heterotopic (subcutaneous) tumor growth in nude mice of U-87 MG cells (tumor weight inhibition, approximately 60%). In contrast, BAY 59-8862 was more active than paclitaxel (P < 0.05 in two of three experiments) in increasing the survival time of mice that were injected orthotopically with U-87 MG cells. The results were supported by the pharmacokinetic data, which indicated a much higher (about 15-fold) brain:plasma level ratio in BAY 59-8862-treated animals compared with paclitaxel-treated animals.

CONCLUSIONS

The study provides evidence of an additional pharmacologic advantage of BAY 59-8862, i.e., the ability to affect the growth of intracranial tumors, probably due to the lack of recognition by the P-glycoprotein-mediated transport systems. The favorable behavior of BAY 59-8862 supports the potential interest in the analog for clinical studies in patients with brain tumors or metastases.