Joshua Thomas

Soft Alkyl Ether Prodrugs of a Model Phenolic Drug: The Effect of Incorporation of Ethyleneoxy Groups on Transdermal Delivery

Two different types of soft alkyl ether prodrugs incorporating ethyleneoxy groups into the promoiety have been synthesized for a model phenol (acetaminophen, APAP): alkyloxycarbonyloxymethyl type (AOCOM) and N-alkyl-N-alkyloxycarbonyl-aminomethyl type (NANAOCAM). The solubilities in isopropyl myristate, SIPM, and water, SAQ, partition coefficients between IPM and pH 4.0 buffer, KIPM:4.0, and the delivery of total species containing APAP through hairless mouse skin from IPM, JMMIPM, have been measured for the prodrugs. The JMMIPM values were accurately predicted by the Roberts-Sloan (RS) equation. Only modest increases in JMMIPM were realized (about 1.4 times) by each type. The only prodrug that was more water soluble and more lipid soluble than APAP did not improve JMMIPM of APAP. This result may be due to the strong association of water molecules with the ethyleneoxy groups, and especially the triethyleneoxy derivative, which dramatically increases the molecular weight and depresses JMMIPM.

Evaluation of alkyloxycarbonyloxymethyl (AOCOM) ethers as novel prodrugs of phenols for topical delivery: AOCOM prodrugs of acetaminophen.

The maximum fluxes of a series of alkyloxycarbonyloxymethyl (AOCOM) ethers of acetaminophen (APAP) through hairless mouse skin from isopropyl myristate, IPM (J(MMIPM)) were measured. The J(MMIPM), solubilities in IPM (S(IPM)), water (S(AQ)) and pH 4.0 buffer (S4.0) and molecular weights MW were then fitted to the Roberts-Sloan (RS) equation: log JM = x + y log S(LIPID) + (1-y) log S(AQ)-zMW. Only one of the prodrugs gave an improvement in the flux obtained by APAP itself. The general lack of improvement in flux seems to be due to the fact that there was no improvement in the S(AQ) values of the AOCOM derivatives compared to APAP. When the n = 5 members of the AOCOM series were added to the n = 66 database of J(MMIPM) to give n = 71 and fitted to the RS equation where S(LIPID) was S(IPM), the following coefficients were obtained: x = -0.562, y = 0.501, z = 0.00248, r2 = 0.923. These results demonstrate the importance of improving S(AQ) for prodrugs to improve their solubilities in the skin and hence the flux of the parent drug. The RS equation, which is derived directly from Ficks law, explains this dependence of flux on S(AQ).

Targeting the Fcμ-receptor in chronic lymphocytic leukemia with a novel IgM-derived antibody-drug conjugate

Fc-receptors (FcR) are widely expressed on cells of the immune system. FcμR is a transmembrane protein with an extracellular Ig-like domain homologous to the FcR for both IgA and IgM (Fcα/μR) and the polymeric Ig receptor (pIgR). FcμR is expressed on CD19+B cells, CD4+/CD8+ T cells, and CD56+/CD3- NK cells. In addition, several groups have reported that FcμR is overexpressed in chronic lymphocytic leukemia (CLL) cells. Using immunofluorescence staining, we found that FcμR can rapidly uptake IgM, internalize it in specific vesicles and transport it through the endocytic pathway to the lysosomal compartment. Interestingly, aggregation of FcμR with IgM leads to rapid internalization of IgM (>80% internalized within 5 minutes) whereas mAb bound FcμR is not internalized. Overexpression on CLL cells and rapid internalization of FcμR represents a potential means of selectively delivering a cytotoxic agent into malignant cells. To this end, we engineered a protein scaffold derived from the CH2-CH3-CH4 IgM constant regions with a C-terminal selenocysteine that allows covalent conjugation of drugs or toxins to the protein scaffold. We verified that the scaffold also binds FcμR, is rapidly internalized and has a serum circulatory half-life comparable to IgM (~18hrs) in NOD/SCID/IL-2Rγnull (NSG) mice. We then demonstrated that the scaffold, when conjugated to a cytotoxic small molecule, kills malignant B cells, but not normal T cells, from CLL patients in vitro and in NSG mice. These findings indicate that the rapid internalization of IgM-FcμR complexes can be exploited for therapeutic purposes. Taken together, IgM-derived protein scaffold antibody-drug conjugates appear as promising treatment modalities for CLL and possibly other malignancies.