Liposomal cisplatin: a new cisplatin formulation

Nanoscale metal-organic frameworks for biomedical imaging and drug delivery

Metal-organic frameworks (MOFs), a class of hybrid materials formed by the self-assembly of polydentate bridging ligands and metal-connecting points, have been studied for a variety of applications. Recently, these materials have been scaled down to nanometer sizes, and this Account details the development of nanoscale metal-organic frameworks (NMOFs) for biomedical applications. NMOFs possess several potential advantages over conventional nanomedicines such as their structural and chemical diversity, their high loading capacity, and their intrinsic biodegradability. Under relatively mild conditions, NMOFs can be obtained as either crystalline or amorphous materials. The particle composition, size, and morphology can be easily tuned to optimize the final particle properties. Researchers have employed two general strategies to deliver active agents using NMOFs: by incorporating active agents into the frameworks or by loading active agents into the pores and channels of the NMOFs. The modification of NMOF surfaces with either silica coatings or organic polymers improves NMOF stability, fine-tunes their properties, and imparts additional functionality. Preliminary biomedical applications of NMOFs have focused on their use as delivery vehicles for imaging contrast agents and molecular therapeutics. Because NMOFs can carry large amounts of paramagnetic metal ions, they have been extensively explored as magnetic resonance imaging (MRI) contrast agents. Both Gd(3+)- and Mn(2+)-containing NMOFs have shown excellent efficacy as T(1)-weighted contrast agents with large per metal- and per particle-based MR relaxivities. Fe(3+)-containing NMOFs have demonstrated excellent T(2)-weighted contrast enhancement. Upon intravenous injection of iron carboxylate NMOFs in Wistar rats, researchers observed negative signal enhancement in the liver and spleen, which dissipated over time, indicating the degradation and clearance of the NMOF. Through the incorporation of luminescent or high Z element building blocks, NMOFs have also served as viable contrast agents for optical imaging or X-ray computed tomography (CT) imaging. Incorporation of membrane impermeable dyes into NMOFs allowed for their uptake by cancer cells and for their controlled release as the framework decomposed. NMOFs have been used to deliver anticancer drugs and other chemotherapeutics. Cisplatin prodrugs were incorporated within NMOFs at exceptionally high levels, either through use of the prodrug as the building block or through attachment of the prodrug onto the framework after synthesis. These NMOFs were encapsulated within a silica shell and targeted to cancer cells. In vitro assays revealed that the targeted NMOFs possessed similar efficacy to cisplatin, while the nontargeted NMOFs were less active. Several different therapeutic molecules were loaded within porous iron-carboxylate NMOFs at unprecedented levels. The NMOF showed sustained drug release with no burst effect, and in vitro assays revealed that the nanoencapsulated drug possessed similar efficacy to the free drug. Although still at a very early stage of development, NMOFs have already shown great promise as a novel platform for nanomedicine. The compositional tunability and mild synthetic conditions used to produce NMOFs should allow for the incorporation of other imaging and therapeutic agents and their effective delivery to targeted cells in vivo.

A phase II study of lipoplatin (liposomal cisplatin)/vinorelbine combination in HER-2/neu-negative metastatic breast cancer

We assessed the efficacy and safety of a liposomal cisplatin (lipoplatin) and vinorelbine combination in metastatic breast cancer (MBC). Thirty-five patients were treated. The objective response rate was 53.1% and the median survival time was 22 months. Grade 3/4 neutropenia was observed in 44% of cycles, and febrile neutropenia was seen in 4 patients (11.4%). No grade 3/4 nephrotoxicity or neuropathy was noted. This combination is effective and well tolerated in patients with MBC and it warrants investigation as first-line treatment.

BACKGROUND

Liposomal cisplatin (lipoplatin) has a mechanism of action similar to that of cisplatin, with reduced toxicities and enhanced or similar efficacy. We wanted to assess the efficacy and safety of a lipoplatin/vinorelbine combination in a phase II clinical trial in metastatic breast cancer (MBC).

METHODS

Thirty-five patients with HER-2/neu-negative (HER-2/neu(-)) MBC were enrolled. Lipoplatin 120 mg/m(2) (days 1, 8, and 15) and vinorelbine 30 mg/m(2) (days 1 and 8) were administered in a 21-day cycle.

RESULTS

Thirty-five patients were included in the intent-to-treat (ITT) analysis; 32 patients were evaluable for response. The objective response rate was 53.1%. Complete response (CR) was achieved in 3 patients (9.4%), partial response (PR) was seen in 14 patients (43.8%), stable disease (SD) was obtained in 12 patients (37.5%), and progressive disease (PD) was seen in 3 patients (9.4%). Median time to disease progression was 8 months (range 6-10 months). After a median follow-up of 15.5 months, 18 patients were still alive; the median survival time was 22 months (95% confidence interval [CI], 14-30). A total of 174 cycles were administered. Neutropenia was the most frequent hematologic toxicity, with grade 3/4 neutropenia observed in 44% of cycles. Febrile neutropenia was observed in 4 patients (11.4%). No grade 3/4 nephrotoxicity or neuropathy was noted. Grade 1/2 nephrotoxicity occurred in 8 patients (22.9%) and grade 3 vomiting was seen in 3 patients (8.6%).

CONCLUSIONS

The results of this trial reveal that vinorelbine/lipoplatin is effective in treating patients with MBC. This regimen is well tolerated with no grade 3/4 nephrotoxicity or neuropathy. The investigation of this regimen as first-line treatment in MBC is warranted.

Drug transporters of platinum-based anticancer agents and their clinical significance

Platinum-based drugs are among the most active anticancer agents and are successfully used in a wide variety of human malignancies. However, acquired and/or intrinsic resistance still represent a major limitation. Lately, in particular mechanisms leading to impaired uptake and/or decreased cellular accumulation of platinum compounds have attracted attention. In this review, we focus on the role of active platinum uptake and efflux systems as determinants of platinum sensitivity and -resistance and their contribution to platinum pharmacokinetics (PK) and pharmacodynamics (PD). First, the three mostly used platinum-based anticancer agents as well as the most promising novel platinum compounds in development are put into clinical perspective. Next, we describe the presently known potential platinum transporters--with special emphasis on organic cation transporters (OCTs)--and discuss their role on clinical outcome (i.e. efficacy and adverse events) of platinum-based chemotherapy. In addition, transporter-mediated tumour resistance, the impact of potential platinum transporter-mediated drug-drug interactions, and the role of drug transporters in the renal elimination of platinum compounds are discussed.