Hyaluronic Acid Analogs

About

Hyaluronic acid (HA) is a large an unsulfated glycosaminoglycan composed of repeating units of N-acetylglucosamine (GlcNAc) and glucuronic acid (GlcA). HA is a high molecular weight (HMW) polymer typically millions of Daltons in size. HA is detected in all tissues with the bulk found deposited in the skin representing almost 50% of the total body HA. The unique properties of HA make it a platform technology, useful in a number of existing commercial products. For example, HA has unique hydrophilic properties with the ability to hold up to a hundred-fold its own weight of water. This hydrating property makes it useful in cosmeceuticals such as skin lotions/creams and dermal fillers. HA also has high viscoelastic properties which are proposed to be of benefit in the synovial fluid of joints where it acts as a lubricant. Through these biophysical properties, and from interactions with receptors such as CD44 and RHAMM, HAs are also believed to play a role in wound healing, cancer and other diseases. Currently the largest HA markets are injectable HA for treating osteoarthritis and dermal fillers for cosmeceutical use with revenues in excess of $1 billion per year. HA has unique biophysical properties making it valuable in a number of existing products. However a major limitation is that when HMW HA degrades into LMW forms it becomes proinflammatory by activating Toll-like Receptor-4 (TLR4). We have now identified analogs of HA which lack this property and prevent native LMW HA from activating TLR4. Thus, N-acylating HA, in particular N-butylation of HA (BHA), removes this proinflammatory property while retaining positive effects of HA. In vitro studies on the macrophage cell line THP1 demonstrated the pro-inflammatory activity of LMW HA through TLR4 activation by stimulating cytokine release. BHA prevented cytokine stimulation by LMW HA as well as gold standard TLR4 agonist LPS-EC. In contrast the TLR2 agonist, PG-PS, produced much smaller cytokine release and this activation was not prevented by BHA, demonstrating that LMW HA and BHA have their effects mediated via TLR4. TLR4 has be demonstrated to be essential for the mouse gout model induced by urate monohydrate injection into joints. Thus we chose this model as a first test for in vivo activity of BHA. In this model, a single 10 µg or 50 µg injection of BHA was given into joints of mice concomitantly with the monosodium urate. These treatments were compared to a standard treatment, colchicine, given prior to inducing the gout as well as after. In this model, BHA had statistically significant benefits on reducing inflammation induced-swelling in treated mice and reduced swelling to control levels (controls received saline injection). In addition both doses of BHA reduced swelling more quickly and to a larger extent than colchicine. These data support the in vitro efficacy data, support the promise of replacing existing HAs, as well as the promise of treating TLR4-mediated diseases. In all a compelling commercial opportunity.