Lymphatic transport and lymph node targeting of methotrexate-conjugated PEGylated dendrimers are enhanced by reducing the length of the drug linker or masking interactions with the injection site.

Drug conjugation to dendrimer-based delivery systems has been shown to enhance delivery to the lymphatic system after subcutaneous administration. Dendrimer interaction with components of the interstitium at the injection site, however, may prevent drainage from the injection site. The current study sought to vary the length of a linker employed to conjugate methotrexate (MTX) to a PEGylated dendrimer, in an attempt to reduce MTX interaction with interstitial binding sites and enhance lymphatic drainage. Dendrimers with shorter linkers resulted in higher lymphatic drainage, presumably via shielding of interaction sites by the PEG mantle, but were not retained in lymph nodes. Improved drainage of dendrimers with longer linkers was achieved through coadministration with dextran to mask interactions at the injection site while maintaining retention within the node. Enhanced drug exposure to the lymph node has the potential to enhance the treatment of lymph-node resident cancer metastases.

The discovery of 1,2,3,9b-tetrahydro-5H-imidazo[2,1-a]isoindol-5-ones as a new class of respiratory syncytial virus (RSV) fusion inhibitors. Part 1.

Respiratory syncytial virus (RSV) is a major cause of respiratory tract infections in infants, young children and adults. Compound 1a (9b-(4-chlorophenyl)-1-(4-fluorobenzoyl)-1,2,3,9b-tetrahydro-5H-imidazo[2,1-a]isoindol-5-one) was identified as an inhibitor of A and B strains of RSV targeting the fusion glycoprotein. SAR was developed by systematic exploration of the phenyl (R(1)) and benzoyl (R(2)) groups. Furthermore, introduction of a nitrogen at the 8-position of the tricyclic core resulted in active analogues with improved properties (aqueous solubility, protein binding and logD) and excellent rat pharmacokinetics (e.g., rat oral bioavailability of 89% for compound 17).

An Orally Available 3-Ethoxybenzisoxazole Capsid Binder with Clinical Activity against Human Rhinovirus.

Respiratory infections caused by human rhinovirus are responsible for severe exacerbations of underlying clinical conditions such as asthma in addition to their economic cost in terms of lost working days due to illness. While several antiviral compounds for treating rhinoviral infections have been discovered, none have succeeded, to date, in reaching approval for clinical use. We have developed a potent, orally available rhinovirus inhibitor 6 that has progressed through early clinical trials. The compound shows favorable pharmacokinetic and activity profiles and has a confirmed mechanism of action through crystallographic studies of a rhinovirus-compound complex. The compound has now progressed to phase IIb clinical studies of its effect on natural rhinovirus infection in humans.

gem-Dihalocyclopropanes as building blocks in natural-product synthesis: enantioselective total syntheses of ent-erythramine and 3-epi-erythramine.

ent-Erythramine ((-)-1), the enantiomer of the alkaloid erythramine, was prepared in 15 steps from known compounds. The first of three pivotal bond-forming steps in the synthesis was a Suzuki-Miyaura cross-coupling reaction of the starting materials to give a bis-silyl ether. The second involved silver(I)-induced electrocyclic ring opening of the gem-dichlorocyclopropane formed in the next step and trapping of the ensuing pi-allyl cation by the tethered nitrogen atom to give, following cleavage of the allyloxycarbonyl protecting group, an approximately 5:6 mixture of the chromatographically separable diastereoisomeric spirocyclic products. In the third critical bond-forming reaction, the iodide formed from one of the diastereoisomers underwent a radical-addition/elimination reaction sequence that led to (-)-1 in 89 % yield. The application of the same sequence of transformations to the other diastereoisomer afforded 3-epi-(+)-erythramine (3-epi-(+)-1).

New protocols for the assembly of the tetracyclic framework associated with the aromatic erythrina alkaloids.

[reaction: see text] Treatment of the anion derived from the ring-fused gem-dichlorocyclopropane 4c with silver tetrafluoroborate afforded the spirocyclic compound 17 in 74% yield. Product 17 was readily converted, over three steps, into the beta-iodoethyl derivative 20 and treatment of this latter compound with n-Bu(3)SnH then afforded, in 93% yield and via a radical addition/elimination sequence, compound 2 incorporating the ABCD framework of the aromatic erythrina alkaloids.

2-Ethoxybenzoxazole as a bioisosteric replacement of an ethyl benzoate group in a human rhinovirus (HRV) capsid binder.

A series of pyridazinylpiperidinyl capsid-binding compounds with novel bicyclic substituents were synthesized and screened against human rhinovirus (HRV). Several 2-alkoxy- and 2-alkylthio-benzoxazole and benzothiazole derivatives showed excellent anti-HRV activity. When tested against a panel of 16 representative HRV types the 2-ethoxybenzoxazole derivative 13 was found to have superior HRV activity (median EC(50) 3.88ng/mL) to known capsid-binders Pleconaril and Pirodavir. Compound 13 illustrates that a 2-alkoxybenzoxazole group can be an effective bioisostere for a benzoate ester or benzaldehyde oxime ether functionality.

An orally bioavailable oxime ether capsid binder with potent activity against human rhinovirus.

A series of capsid-binding compounds was screened against human rhinovirus (HRV) using a CPE based assay. The ethyl oxime ether 14 was found to have outstanding anti-HRV activity (median IC(50) 4.75 ng/mL), and unlike the equivalent ethyl ester compound 3 (Pirodavir), it has good oral bioavailability, making it a promising development candidate. Compound 14 illustrates that an oxime ether group can act as a metabolically stable bioisostere for an ester functionality.