Early development evaluation of AZD8081: a substrate for the NK receptors

A case study where pharmaceutical salts were used to address the issue of low in vivo exposure

The present active pharmaceutical ingredient (API) is a lipophilic compound with a significant risk of not achieving therapeutic plasma concentrations due to solubility-limited absorption. The aim of the presented studies was to investigate whether three novel salts of a new selected candidate in the cardiovascular therapy area could be applied to improve intestinal absorption and the subsequent in vivo exposure. Three salts (chloride, hydrogen sulfate, and hemi-1.5-naphtalenedisulphonate) of the compound were manufactured and investigated regarding solubility, dissolution rate, and in vivo exposure in rats. The chemical and physical stability of the salt forms (and the crystalline parent compound) were followed in solid state, when dissolved and when formulated as microsuspensions. All salts showed improved solubility in investigated media, increased dissolution rate, and elevated in vivo exposures compared to a nanocrystal formulation (top-down) of the parent free base of the compound. The chloride- and the hydrogen sulfate salts of the API showed similar patterns regarding the chemical stability in solid state as the crystalline free base, while the salt formed of the hemi-1.5-naphtalenedisulphonic acid showed significantly improved stability. In conclusion, this study showed that three salts of a new selected candidate drug could be used to improve solubility, increase dissolution rate, and enhance oral absorption compared with a more commonly used nanocrystal formulation of the API. However, the identity of the counter ion appeared to be of less importance. On the other hand, only the salt of the hemi-1.5-naphtalenedisulphonic acid seemed to improve chemical stability compared with the API.

Preformulation investigation and challenges; salt formation, salt disproportionation and hepatic recirculation

A compound, which is a selective peroxisome proliferator activated receptor (PPAR) agonist, was investigated. The aim of the presented studies was to evaluate the potential of the further development of the compound. Fundamental physicochemical properties and stability of the compound were characterized in solution by liquid chromatography and NMR and in solid-state by various techniques. The drug itself is a lipophilic acid with tendency to form aggregates in solution. The neutral form was only obtained in amorphous form with a glass-transition temperature of approximately 0°C. The intrinsic solubility at room temperature was determined to 0.03mg/mL. Chemical stability studies of the compound in aqueous solutions showed good stability for at least two weeks at room temperature, except at pH1, where a slight degradation was already observed after one day. The chemical stability in the amorphous solid-state was investigated during a period of three months. At 25°C/60% relative humidity (RH) and 40°C/75% RH no significant degradation was observed. At 80°C, however, some degradation was observed after four weeks and approximately 3% after three months. In an accelerated photostability study, degradation of approximately 4% was observed. Attempts to identify a crystalline form of the neutral compound were unsuccessful, however, salt formation with tert-butylamine, resulted in crystalline material. Results from stability tests of the presented crystalline salt form indicated improved chemical stability at conditions whereas the amorphous neutral form degraded. However, the salt form of the drug dissociated under certain conditions. The drug was administered both per oral and intravenously, as amorphous nanoparticles, to conscious dogs. Plasma profiles showed curves with secondary absorption peaks, indicating hepatic recirculation following both administration routes. A similar behavior was observed in rats after oral administration of a pH-adjusted solution. The observed double peaks in plasma exposure and the dissociation tendency of the salt form, were properties that contributed to make further development of the candidate drug challenging. Options for development of solid dosage forms of both amorphous and crystalline material of the compound are discussed.

The possible link between the elevated serum levels of neurokinin A and anti-ribosomal P protein antibodies in children with autism

BACKGROUND

Neurogenic inflammation is orchestrated by a large number of neuropeptides. Tachykinins (substance P, neurokinin A and neurokinin B) are pro-inflammatory neuropeptides that may play an important role in some autoimmune neuroinflammatory diseases. Autoimmunity may have a role in the pathogenesis of autism in some patients. We are the first to measure serum neurokinin A levels in autistic children. The relationship between serum levels of neurokinin A and anti-ribosomal P protein antibodies was also studied.

METHODS

Serum neurokinin A and anti-ribosomal P protein antibodies were measured in 70 autistic children in comparison to 48 healthy-matched children.

RESULTS

Autistic children had significantly higher serum neurokinin A levels than healthy controls (P < 0.001). Children with severe autism had significantly higher serum neurokinin A levels than patients with mild to moderate autism (P < 0.001). Increased serum levels of neurokinin A and anti-ribosomal P protein antibodies were found in 57.1% and 44.3%, respectively of autistic children. There was significant positive correlations between serum levels of neurokinin A and anti-ribosomal P protein antibodies (P = 0.004).

CONCLUSIONS

Serum neurokinin A levels were elevated in some autistic children and they were significantly correlated to the severity of autism and to serum levels of anti-ribosomal P protein antibodies. However, this is an initial report that warrants further research to determine the pathogenic role of neurokinin A and its possible link to autoimmunity in autism. The therapeutic role of tachykinin receptor antagonists, a potential new class of anti-inflammatory medications, should also be studied in autism.