RAFT-Derived Polymer-Drug Conjugates: Poly(hydroxypropyl methacrylamide) (HPMA)-7-Ethyl-10-hydroxycamptothecin (SN-38) Conjugates

A series of well-defined polymer-drug conjugates were prepared in order to modify the physical properties of a known cytotoxic drug, 7-ethyl-10-hydroxycamptothecin (SN-38), the active metabolite of irinotecan (CPT-11). Reversible addition-fragmentation chain transfer (RAFT) polymerisation was used to covalently and site-specifically append a defined N-(2-hydroxypropyl)methacrylamide (HPMA) polymer to SN-38 using a graft-from process. These poly-HPMA-SN-38 conjugates displayed excellent aqueous solubility and stability, whilst retaining the cytotoxic activity of the parent SN-38. Invitro co-culture assays containing both cancer and noncancer cell lines demonstrated the specificity of RAFT-derived poly-HPMA-SN-38 conjugates for cancerous cells. The concept of post-optimisation modification of small-molecule drugs through a graft-from polymer conjugation method is introduced.