Tofimilast is a potent phosphodiesterase-4 (PDE4) inhibitor with low oral bioavailability and no emesis-associated behaviors in ferrets at plasma concentrations up to 152 ng/ml. Tofimilast exhibited an apparent slower absorption through the rat lung after administration as a dry powder, although absorption half-life values were <1 h and therefore the significance of a formulation effect for this compound is questionable. Tofimilast was tested as a therapeutic agent against asthma and chronic obstructive pulmonary disease but development has been discontinued due to lack of efficacy.

Bristol-Myers Squibb developed BMS-919373, a selective IKur inhibitor for use in atrial fibrillation, acute coronary syndromes, and paroxysmal atrial fibrillation. IKur is a repolarizing K+ current encoded by the KCNA5 gene and is expressed predominantly in the atrium of human. IKur is a potential atrial-selective target for the treatment of atrial fibrillation. BMS-919373 participated in phase II clinical trials to evaluate the effect on atrial fibrillation burden in patients with paroxysmal atrial fibrillation. In addition, in phase I clinical trials for patients with acute coronary syndromes. However, further, developments have been discontinued.

KX-02 is a compound demonstrating dual inhibitory activity against Src kinase and tubulin polymerization. It readily crosses the blood-brain-barrier in mice. It is under development for the treatment of solid tumors.