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Nitisinone inhibits the cytochrome P450 (CYP) subfamilies CYP2C9, CYP2D6, and CYP2E1 and the organic anion transporter (OAT) isoforms OAT1 and OAT3 in vitro. Since the effect of nitisinone on these enzymes and transporters in humans is still unknown, the purpose of this study was to evaluate the effect of nitisinone on these CYP subfamilies and OAT isoforms. This was an open-label, nonrandomized, two-arm, phase 1 study (EudraCT: 2016-004297-17) in healthy volunteers. The substrates (tolbutamide, metoprolol, and chlorzoxazone for the respective CYPs and furosemide for the OATs) were administered as single doses, before and after 15 days of once daily dosing of 80 mg nitisinone, to determine the AUC∞ ratios ([substrate+nitisinone]/[substrate]). Nitisinone pharmacokinetics, safety, and tolerability were also assessed, and blood and urine were collected to determine substrate and nitisinone concentrations by LC-MS/MS. Thirty-six subjects were enrolled with 18 subjects included in each arm. The least square mean ratio (90% confidence interval) for AUC∞ was 2.31 (2.11–2.53) for tolbutamide, 0.95 (0.88–1.03) for metoprolol, 0.73 (0.67–0.80) for chlorzoxazone, and 1.72 (1.63–1.81) for furosemide. Clinically relevant nitisinone steady-state concentrations were reached after 12 days: mean Cav,ss of 94.08 μM. All treatments were well tolerated, and no safety concerns were identified. Nitisinone did not affect CYP2D6 activity, was a weak inducer of CYP2E1, and was a weak inhibitor of OAT1 and OAT3. Nitisinone was a moderate inhibitor of CYP2C9, and treatment may therefore result in increased plasma concentrations of comedications metabolized primarily via this enzyme. EudraCT 2016-004297-17.

Dexmecamylamine (TC-5214) is a nicotinic channel modulator that was evaluated as a potential adjunct treatment to an antidepressant for patients with major depressive disorder. Dexmecamylamine is almost completely eliminated via the kidneys, with more than 90 % of a given dose excreted unchanged in urine. The aim of this study was to assess the single-dose pharmacokinetics of dexmecamylamine in subjects with various degrees of renal impairment and subjects undergoing hemodialysis. A single-dose, open-label, parallel-group study was conducted at two study centers in the USA. There were four treatment groups with eight subjects in each, receiving a single dose of dexmecamylamine 8 mg (subjects with normal renal function and mild renal impairment) or TC-5412 2 mg [subjects with moderate renal impairment and end-stage renal disease (ESRD)]. The pharmacokinetics of dexmecamylamine in plasma, urine, and dialysate were evaluated using non-compartmental analysis. The plasma pharmacokinetics of dexmecamylamine were influenced by renal function. The increase in dose–normalized area under the plasma concentration–time curve (AUC) was statistically significant with an approximately doubled exposure in subjects with moderate renal impairment compared with subjects with normal renal function. The maximum plasma concentration was not impacted by renal function. Plasma clearance of dexmecamylamine in ESRD subjects appeared negligible, with flat plasma concentration–time profiles. Hemodialysis had a relatively modest effect on reduction of dexmecamylamine plasma concentrations. There was no discernable relationship between renal clearance and urinary pH. Renal impairment increased the AUC, prolonged the elimination half-life, and decreased the clearance of dexmecamylamine following administration as a single oral dose. It is likely that renal function would need to be taken into account when setting the dose. Dexmecamylamine administration should be avoided or the dose significantly reduced in patients with severe renal impairment and ESRD.

A 57-year-old man and a 70-year-old woman with relapsing polychondritis are reported. The man, suffering from arthralgias, respiratory obstruction, external ear and sanddle-nose deformities, conjunctivitis and irido-cyclitis, died after 4 years from airway obstruction because of tracheal and bronchial collapse. The woman is alive 8 months after the development of respiratory obstruction, probably caused by radiographically demonstrated tracheal obstruction, a saddle-nose deformity and hearing impairment. Microscopically, the involved cartilages showed degenerative and slight inflammatory changes and were eventually replaced by fibrous tissue. Histochemical studies, utilizing staining with Alcian blue at controlled electrolyte concentrations (Scott technique) and at controlled pH:s, with or without digestion with bacterial chondroitinase ABC; and staining with the PAS-method, with or without diastase digestion, revealed a complete or relative loss of glucosaminoglycans and glycogen. A biosynthetic defect is considered unlikely to be the primary pathogenetic mechanism of relapsing polychondritis. Histological and histochemical examination of biopsies from involved cartilages contribute to a definite diagnosis.