Apocynin, also known as acetovanillone, is a natural organic compound related to vanillin. It has been isolated from a variety of plant sources. Metabolites of apocynin are able to block the activity of NADPH oxidase, thus giving apocynin antioxidant and anti-inflammatory capabilities. Effects of apocynin on the concentration of reactive oxygen and nitrogen species in patients with asthma and chronic obstructive pulmonary disease were investigated in phase I clinical trials. In preclinical models, it was found that apocynin provides neuroprotective effects in models of stroke and Parkinson's disease.

Thiorphan is the first potent synthetic inhibitor of enkephalinase. Thiorphan displays antinociceptive activity after systemic administration. Thiorphan also inhibits to a lesser extent the widely distributed angiotensin-converting enzyme, a carboxydipeptidase implicated in blood pressure regulation. Thiorphan failed to potentiate allergen-induced airway responses in asthma. Thiorphan significantly reduced the castor oil-induced diarrhea in rats when administered intravenously but not when administered intracerebroventricularly. Racecadotril, via its active metabolite thiorphan, was consistently effective in animal models and patients with various forms of acute diarrhea by inhibiting pathologic (but not basal) secretion from the gut without changing gastro-intestinal transit time or motility.

Bimosiamose, discovered by Encysive Pharmaceutical and presently being developed by Revotar Biopharmaceuticals, is an 863 g/mol molecular weight dimer with minimal carbohydrate content and is, to date, the leading selectin inhibitor in clinical development. It was developed as anti-inflammatory drug fir the treatment of acute chronic inflammatory disorders including COPD. This compound has shown promise in a phase IIa 'proof of concept' trial in patients with asthma, reducing airway recruitment of eosinophils after intravenous administration. In acute lung injury, neutrophils (a type of white blood cells, thus belonging to the group of cells of the body’s defence system-the immune system) are drawn to the small lung bloodvessels and migrate into the air sacs (alveoli). There they release substances, which cause the inflammation leading to further destruction of the lung tissue. Bimosiamose disodium is expected to hinder the migration of these neutrophils into the alveoli.

Isbufylline is a xanthine derivative. This compound exhibits remarkable antibronchospastic properties both in in vitro and in vivo (after oral or intravenous administration) experimental models. Isbufylline is significantly more effective than theophylline in antagonizing bronchospasms elicited by spasmogens (capsaicin, arachidonic acid, PAF and antigen) which mainly act by a local release of biologically active substances proposed to be involved in the pathogenesis of asthma. Isbufylline, unlike theophylline, possesses little or no CNS excitatory properties. Isbufylline exerts a greater inhibitory activity than theophylline on total phosphodiesterase activity in the rat lung.

Potassium guaiacolsulfonate also known as sulfoguaiacolum is a salt of GUAIACOLSULFONIC ACID, which is used as an expectorant, to relieve symptoms of cough and mucus in the chest due to respiratory infections, asthma, colds, or hay fever. It works by thinning mucus (phlegm) in the lungs, making it less sticky and easier to cough up. This reduces chest congestion by making coughs more productive.

Amelubant, its metabolite BIIL 260 (formed by removal of the ethoxycarbonyl protecting group), and its major metabolite BIIL 315 (formed by removal of the protecting group and glucuronidation) had potent in vitro and in vivo Leukotriene B4 receptor antagonistic properties. Amelubant has been in phase II clinical trials by Boehringer Ingelheim for the treatment of cystic fibrosis, chronic obstructive pulmonay disease, bronchial asthma and rheumatoid arthritis. However, this research has been discontinued. In 2002, orphan drug designation was received in E.U. for the treatment of cystic fibrosis. Serious adverse events of Amelubant were characterized by increased presentation of respiratory signs and/or symptoms associated with pulmonary exacerbation and resulted in admission to a hospital and/or administration of IV antibiotics.

Veliflapon (BAY X1005, DG-031) is an enantioselective inhibitor of 5-lipoxygenase activating protein, or FLAP. There are variants in the gene encoding FLAP, and the gene encoding leukotriene A4 hydrolase (LTA4H) linked to risk of heart attack. These variants appear to confer increased risk of heart attack by increasing the production of leukotriene B4 (LTB4), a potent driver of inflammation produced in atherosclerotic plaques. deCODE licensed veliflapon (BAY X1005, DG-031) from Bayer AG, which developed it originally for the treatment of asthma.

MK-0359 (L-454560) is a selective and potent type 4 phosphodiesterases (PDE4) inhibitor, which binds to both the apo-(Mg2+-free) and holoenzyme states of PDE4. This compound successfully has passed the phase II clinical trial for the treatment of asthma, Pulmonary Disease, Chronic Obstructive (COPD) and Rheumatoid Arthritis. However, there is no information about the further research of this drug.

TG-100115 is a potent dual inhibitor of PI3K-gamma and PI3K-delta. TG-100115 has broad anti-inflammatory activities. TG-100115 provided potent cardioprotection, reducing infarct development and preserving myocardial function. In murine models of asthma and acute stages of chronic obstructive pulmonary disease, aerosolized TG100-115 demonstrated not only markedly inhibited anti-inflammatory activity but also, in the case of the asthma model, improved functional outcome for the test animals. TG-100115 can be used as a potent TRPM7 kinase inhibitor and a potent inhibitor of breast cancer cell migration.

(R)-Mequitazine or V0162 (10-[(3R)-1-azabicyclo[2.2.2]oct-3-ylmethyl]-10H-phenothiazine) is an anticholinergic enantiomer of mequitazine, an existing oral racemic antihistamine commercialized for over 30 years. (R)-Mequitazine was found to be an antagonist at muscarinic acetylcholine receptors behaving as an inverse agonist. (R)-Mequitazine was investigated in clinical trials for the treatment of chronic obstructive pulmonary disease, asthma and urinary incontinence.