Pharmaceutical Development of a Parenteral Lyophilized Formulation of the Investigational Polymer-Conjugated Platinum Anticancer Agent AP 5280

Metal-containing and related polymers for biomedical applications

A survey of the most recent progress in the biomedical applications of metal-containing polymers is given. Due to the unique optical, electrochemical, and magnetic properties, at least 30 different metal elements, most of them transition metals, are introduced into polymeric frameworks for interactions with biology-relevant substrates via various means. Inspired by the advance of metal-containing small molecular drugs and promoted by the great progress in polymer chemistry, metal-containing polymers have gained momentum during recent decades. According to their different applications, this review summarizes the following biomedical applications: (1) metal-containing polymers as drug delivery vehicles; (2) metal-containing polymeric drugs and biocides, including antimicrobial and antiviral agents, anticancer drugs, photodynamic therapy agents, radiotherapy agents and biocides; (3) metal-containing polymers as biosensors, and (4) metal-containing polymers in bioimaging.

ProLindac (AP5346): a review of the development of an HPMA DACH platinum Polymer Therapeutic

ProLindac (AP5346) is DACH (diaminocyclohexane) platinum polymer prodrug currently in phase II clinical development. It uses a 25 kDa polymer delivery vehicle based on hydroxypropylmethacrylamide (HPMA) to target the active form of the approved drug oxaliplatin to tumors. The pH-sensitive linker that binds platinum to the polymer releases platinum more rapidly in low pH environments, as found typically in many tumors. This review summarizes the development of ProLindac to date, including preclinical efficacy studies, the phase I monotherapy clinical study in patients with solid tumors, and the phase I/II monotherapy study in patients with recurrent ovarian cancer. Both preclinical and clinical study data indicate that ProLindac exhibits efficacy at least equal to, and likely superior to oxaliplatin, while demonstrating excellent tolerability. Additional clinical studies of ProLindac used in combination with other chemotherapeutic agents are planned.

Development of HPMA copolymer-anticancer conjugates: clinical experience and lessons learnt

The concept of polymer-drug conjugates was proposed more than 30 years ago, and an N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer conjugate of doxorubicin covalently bound to the polymer backbone by a Gly-Phe-Leu-Gly peptidyl linker (FCE28068) became the first synthetic polymer-based anticancer conjugate to enter clinical trial in 1994. This conjugate arose from rational design attempting to capitalise on passive tumour targeting by the enhanced permeability and retention effect and, at the cellular level, lysosomotropic drug delivery to improve therapeutic index. Early clinical results were promising, confirming activity in chemotherapy refractory patients and the safety of HPMA as a new polymer platform. Subsequent Phase I/II trials have investigated an HPMA copolymer-based conjugate containing a doxorubicin and additionally galactose as a targeting moiety to promote liver targeting (FCE28069), and also HPMA copolymer conjugates of paclitaxel (PNU 166945), camptothecin (PNU 166148) and two platinates (AP5280 and AP5346- ProLindac). The preclinical and clinical observations made in these, and clinical studies with other polymer conjugates, should shape the development of next generation anticancer polymer therapeutics.

Assessment of performance of manufacturing procedures in a unit for production of investigational anticancer agents, using a mixed effects analysis

Purpose

To identify the magnitude and sources of variability of a generic, aseptic manufacturing process for experimental anticancer agents employed at our facility, and to estimate the effects on product quality.

Materials and Methods

In-process and quality control data of all products manufactured according to this generic process (composed of weighing, dissolution, filtration, filling, semi-stoppering and lyophilization) over a 3-year period were retrospectively analyzed using mixed-effects analysis.

Results

Variability in the filling process was shown to be marginal and of minor importance for product quality in terms of content and content uniformity. An overall content of 101% was found with batch-to-batch and vial-to-vial variability up to 4.21% and 2.57%, respectively. Estimation of the overall batch failure revealed that structural bias in content and a high batch-to-batch variability in content were the most prominent factors determining batch failure. Furthermore, content and not content uniformity was shown to be most important parameter influencing batch failure. Calculated Process Capability Indices (CpKs) calculated for each product showed that the process is capable of manufacturing products which will routinely comply with the specification of 90–110% for content. However, the CpK values decreased dramatically using the specification of 95–105% as required for approved drug products.

Conclusion

These results indicate that at the early stage of product development less tight specification limits must be applied to prevent unnecessary batch rejection of investigational agents.

A Phase I and Pharmacological Study of the Platinum Polymer AP5280 Given as an Intravenous Infusion Once Every 3 Weeks in Patients with Solid Tumors

PURPOSE

This Phase I study was designed to determine the maximum tolerated dose, profile of adverse events, and dose-limiting toxicity of AP5280 in patients with solid tumors. Furthermore, the platinum (Pt) pharmacokinetics after AP5280 administration and preliminary antitumor activity were evaluated. AP5280 is a Pt agent linked to the water-soluble, biocompatible copolymer N-(2-hydroxypropyl)methacrylamide, which potentially increases Pt accumulation in tumors via the enhanced permeability and retention effect. In this way, it is anticipated that a higher activity of therapeutic Pt can be reached. The pharmaceutical product contains approximately 8.5% of Pt by weight and has a molecular weight of approximately 25,000.

EXPERIMENTAL DESIGN

Adult patients with solid tumors received AP5280 as a 1-h i.v. infusion every 21 days. Pharmacokinetics of total and unbound Pt were determined during the first treatment course and before the start of each new cycle using noncompartmental pharmacokinetic analysis. Pt-DNA adduct concentrations in WBCs and, if available, in tumor tissue were quantified using a sensitive (32)P postlabeling assay.

RESULTS

Twenty-nine patients were treated at eight dose levels (90-4500 mg Pt/m(2)). The dose-limiting toxicity was Common Toxicity Criteria grade 3 vomiting and was experienced at 4500 mg Pt/m(2) in two of six patients. The maximum tolerated dose on this schedule was therefore 4500 mg Pt/m(2), and the recommended dose for a Phase II study is 3300 mg Pt/m(2). Renal toxicity and myelosuppression, toxicities typically observed with cisplatin and carboplatin, were minimal for AP5280. The area under the curve of total Pt increased with increasing AP5280 dose. Plasma clearance of total Pt was 644 +/- 266 ml/h, and the terminal half-life was 116 +/- 46.2 h. After AP5280 administration, Pt-guanine-guanine DNA adduct concentrations in WBCs ranged from 70 to 1848 amol/microg DNA, concentrations that were substantially lower than concentrations measured after administration of therapeutic doses of cisplatin.

CONCLUSIONS

AP5280 can be administered safely as a 1-h i.v. infusion at a dose of 3300 mg Pt/m(2) once every 3 weeks and produces prolonged plasma exposure compared with any of the free Pt-containing drugs. However, it remains to be determined whether AP5280 can actually increase Pt delivery to the DNA of tumor cells in man as has been shown in experimental models.