Akira Okamachi

Novel hyaluronic acid-methotrexate conjugates for osteoarthritis treatment.

Hyaluronic acid (HA) provides synovial fluid viscoelasticity and has a lubricating effect. Injections of HA preparations into the knee joint are widely used as osteoarthritis therapy. The current HA products reduce pain but do not fully control inflammation. Oral methotrexate (MTX) has anti-inflammatory efficacy but is associated with severe adverse events. Based on the rationale that a conjugation of HA and MTX would combine the efficacy of the two clinically evaluated agents and avoid the risks of MTX alone, we designed HA-MTX conjugates in which the MTX connects with the HA through peptides susceptible to cleavage by lysosomal enzymes. Intra-articular injection of our HA-MTX conjugate (conjugate 4) produced a significant reduction of the knee swelling in antigen-induced arthritis rat, whereas free MTX, HA or a mixture of HA and MTX showed no or marginal effects on the model. The efficacy of conjugate 4 was almost the same as that of MTX oral treatment. Conjugate 4 has potential as a compound for the treatment of osteoarthritis.

Synthesis and optimization of hyaluronic acid-methotrexate conjugates to maximize benefit in the treatment of osteoarthritis.

We previously reported that a conjugate of hyaluronic acid (HA) and methotrexate (MTX) could be a prototype for future osteoarthritis drugs having the efficacy of the two clinically validated agents but with a reduced risk of the systemic side effects of MTX by using HA as the drug delivery carrier. To identify a clinical candidate, we attempted optimization of a lead, conjugate 1. Initially, in fragmentation experiments with cathepsins, we optimized the peptide part of HA-MTX conjugates to be simpler and more susceptible to enzymatic cleavage. Then we optimized the peptide, the linker, the molecular weight, and the binding ratio of the MTX of the conjugates to inhibit proliferation of human fibroblast-like synoviocytes in vitro and knee swelling in rat antigen-induced monoarthritis in vivo. Consequently, we found conjugate 30 (DK226) to be a candidate drug for the treatment of osteoarthritis.

AMIDATION OF HYALURONIC ACID WITH A METHOTREXATE-DERIVED AMINE: OPTIMIZATION OF THE KEY REACTION FOR THE SYNTHESIS OF A CANDIDATE DRUG FOR THE TREATMENT OF OSTEOARTHRITIS

Optimal amidation conditions between hyaluronic acid (HA) and a methotrexate (MTX)-derived amine that gave rise to a HA-MTX conjugate having a molecular weight of ~2000 kDa have been established based on a model experiment using a tryptophan-derived amine in aqueous THF. This method is robust and provides a conjugate with properties of primary importance for efficacy-MW and amine binding ratio—that satisfy the criteria for a HA-MTX conjugate to be a good candidate.

Design and Synthesis of Novel Pure Motilin Antagonists

Motilin is a 22 amino acid gastrointestinal (GI) peptide which stimulates contractile activity of gastrointestinal smooth muscle. Recently, it was suggested that motilin may be involved in the production of some GI symptoms, such as early satiety, abdominal distention, nausea, vomiting, and anorexia, suggesting that motilin antagonists may have clinical applications.