It takes years of hard work and luck to obtain a highly selective small molecule drug. Alternatively, a delivery system properly tailored to carrying potent antitumor drugs can be used. In the mid-1970s, Ringsdorf proposed covalently attaching chemotherapeutic agents to water soluble synthetic polymers for the first time. The advantages of using such polymers are:

• Increased solubility and stability of hydrophobic drugs.
• More drug delivered to the tumor tissue.
• Enhanced tumor specificity by the addition of a targeting residue.
• Fewer undesirable side effects and reduced frequency of dosing.

Human albumin (HA), polyglutamic acid (PGA), N-hydroxymethyl methacrylamide copolymer (HPMA), poly(lactic-co-glycolic acid) (PLGA), and PEG have been widely tested. CellMosaic helps biopharmaceutical companies developing target-specific small molecule drug conjugates using these classical polymers. 

Case Studies:

1. Loading hydrophobic drugs onto a hydrophilic polymer at CellMosaic (shown below).
• Challenge: Very hydrophobic small molecule drugs. The drug has serveral 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.