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Targeted drug delivery via the folate receptor
1Division of Pharmaceutics and Pharmaceutical Chemistry, College of Pharmacy, The Ohio State University, Rm 542 LM Parks Hall, 500 W. 12th Ave., Columbus, OH, 43210, USA.
Abstract:
The folate receptor is a highly selective tumor marker overexpressed in greater than 90% of ovarian carcinomas. Two general strategies have been developed for the targeted delivery of drugs to folate receptor-positive tumor cells: by coupling to a monoclonal antibody against the receptor and by coupling to a high affinity ligand, folic acid. First, antibodies against the folate receptor, including their fragments and derivatives, have been evaluated for tumor imaging and immunotherapy clinically and have shown significant targeting efficacy in ovarian cancer patients. Folic acid, a high affinity ligand of the folate receptor, retains its receptor binding properties when derivatized via its gamma-carboxyl. Folate conjugation, therefore, presents an alternative method of targeting the folate receptor. This second strategy has been successfully applied in vitro for the receptor-specific delivery of protein toxins, anti-T-cell receptor antibodies, interleukin-2, chemotherapy agents, gamma-emitting radiopharmaceuticals, magnetic resonance imaging contrast agents, liposomal drug carriers, and gene transfer vectors. Low molecular weight radiopharmaceuticals based on folate conjugates showed much more favorable pharmacokinetic properties than radiolabeled antibodies and greater tumor selectivity in folate receptor-positive animal tumor models. The small size, convenient availability, simple conjugation chemistry, and presumed lack of immunogenicity of folic acid make it an ideal ligand for targeted delivery to tumors.
Insights
Folic acid, a high-affinity ligand, offers a promising strategy for targeted drug delivery to folate receptor-positive ovarian cancers. This approach demonstrates superior tumor selectivity and pharmacokinetics compared to antibody-based methods.
Area of Science:
- Oncology
- Molecular Biology
- Drug Delivery
Background:
- The folate receptor is overexpressed in over 90% of ovarian carcinomas, making it a selective tumor marker.
- Targeted drug delivery strategies aim to enhance therapeutic efficacy and minimize systemic toxicity.
- Two main strategies involve using monoclonal antibodies or folic acid to target the folate receptor.
Purpose of the Study:
- To evaluate folic acid conjugation as a method for targeted drug delivery to folate receptor-positive tumors.
- To compare the efficacy and pharmacokinetic properties of folate conjugates with antibody-based targeting.
Main Methods:
- Review of clinical and in vitro studies evaluating antibody-based folate receptor targeting.
- Assessment of in vitro and in vivo studies utilizing folic acid conjugates for drug delivery.
- Analysis of pharmacokinetic and tumor selectivity data for both targeting strategies.
Main Results:
- Antibodies against the folate receptor have shown clinical targeting efficacy in ovarian cancer.
- Folic acid retains receptor binding properties when derivatized and can be used for targeted delivery of various agents.
- Folate conjugates, particularly low molecular weight radiopharmaceuticals, exhibited favorable pharmacokinetics and greater tumor selectivity than radiolabeled antibodies in preclinical models.
Conclusions:
- Folic acid conjugation is a viable and effective alternative strategy for targeting folate receptor-positive tumors.
- The characteristics of folic acid, including its small size, availability, and simple conjugation chemistry, make it an ideal ligand for targeted cancer therapy.
- Folate-based targeting holds significant potential for improving drug delivery and therapeutic outcomes in ovarian cancer and other folate receptor-expressing malignancies.