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Polymer-Small Molecule Drug Conjugate

As an alternative to the many years of work—and good fortune—often required to develop a highly selective small-molecule drug, a properly designed delivery system can be used to carry potent antitumor agents. In the mid-1970s, Ringsdorf, a polymer chemist, first proposed the concept of covalently attaching chemotherapeutic agents to water-soluble synthetic polymers.

Advantages of using polymers to deliver chemotherapeutic agents:

• Increased solubility and stability of hydrophobic drugs.
• Greater drug accumulation in tumor tissue.
• Enhanced tumor specificity through the addition of targeting residues.
• Fewer side effects and reduced dosing frequency.

CellMosaic® assists biopharmaceutical companies in developing target-specific small molecule drug conjugates using classical polymer carriers. Human albumin (HA), polyglutamic acid (PGA), N-hydroxymethyl methacrylamide copolymer (HPMA), poly(lactic-co-glycolic acid) (PLGA), and PEG are among the polymers widely tested for these applications.

Case Studies:

1. Loading hydrophobic drugs onto a hydrophilic polymer at CellMosaic® (shown below).
   • Challenge: Very hydrophobic small molecule drugs. The drug has several OH groups that may interfere with the conjugation. The loading capacity onto the polymer needs to be as high as 20% (w/w).
   • Modification strategies for small drugs: Small drugs were first modified site-specifically with a single reactive amine group. 
   • Result: 20% drugs are loaded onto the polymer (w/w) without any precipitation in water. The procedure is easy to scale up.