Relation Between Blood Concentration of Colchicine and Response to Colchicine Treatment in Gout Flare
Relation Between Blood Concentration of Colchicine and Response to Colchicine Treatment in Gout Flare
Gout, secondary to sodium urate crystal deposition, is responsible of recurrent inflammatory
 painful flares. Efficacy of colchicine which is the first line drug for the treatment and
 prophylaxis of gout flare varies and only half of treated patients experience good response.
 This study aims to optimize colchicine prescription for the treatment and prophylaxis of gout
 flare.

 Current data suggest that efficiency of colchicine relies on its maximum blood concentration
 (Cmax).

 In this study, the investigators hypothesize that responders to colchicine treatment have
 higher colchicine Cmax than non-responder patients following the recommended dose regimen (1
 mg then 0.5 mg 1 hour later).

 The individual pharmacokinetics (PK) of colchicine remains poorly investigated while the
 assessment of individual drug metabolisms can be performed.

 The hypothesis of this study stands that several factors contribute to the variability of
 colchicine Cmax. The analysis of individual PK profile and a well-characterized metabolism of
 colchicine will permit a personalized treatment regimen for the treatment and prophylaxis of
 gout flares.
Gout flare is driven by interleukin (IL)-1β production and can be treated by colchicine,
 NSAID, corticoid or IL-1β blockers (PMID 27457514).

 Colchicine is an alkaloid compound that disrupts cytoskeletal functions through inhibition of
 microtubule polymerization and consequently interferes with the intracellular assembly of the
 inflammasome NLRP3 complex that mediates activation of IL-1β (PMID 16407889).

 Efficacy of colchicine treatment in gout flare varies between 37.5 and 64% (PMID 3314832;
 20131255). Previous study suggests that colchicine efficiency relies on its blood maximum
 concentration (Cmax) (PMID 20131255). However this hypothesis needs to be confirmed.

 The hypothesis of this study stands that colchicine Cmax varies with individual colchicine
 pharmacokinetics and that this individual variation may explain the variation response of
 colchicine treatment.

 Absorption of orally administrated colchicine varies between 24 et 88% with an average of
 45%. Thus, following oral administration of 1.8 mg colchicine over 1 hour to healthy young
 adults, under fasting condition, the colchicine Cmax (mean 6.2 ng/ml) is reached within a
 median of 1.8 hours (range 1.0-2.5) (PMID 20131255).

 Colchicine is demethylated to two metabolites, 2-O-demethylcolchicine and
 3-O-demethylcolchicine (2- and 3-DMC, respectively). In vitro studies have shown that hepatic
 cytochrome P450 3A4 (CYP3A4) is involved in the metabolism of colchicine to 2- and 3-DMC.
 Colchicine is also a substrate of liver and intestinal P-glycoprotein (P-gp) transporter.

 Colchicine is eliminated in urine and stools. 40-65% of orally administrated colchicine is
 recovered unchanged in urine. Enterohepatic recirculation and biliary excretion account for
 around 50% of colchicine elimination. The mean half-live elimination is 20 to 40 hours.

 Thus, blood concentration of colchicine depends on kidney and hepatic functions, intestinal
 absorption and secretion, the presence of drug-drug interactions and individual
 characteristics of CYP3A4 and P-gp activities (PMID 21480191).

 The individual CYP3A4 and P-gp activities can be assessed with specific probe and/or
 substrate of these proteins in the so-called phenotyping assay. Thus, using micro dose of
 midazolam and fexofenadine the activity of CYP3A4 and P-gp, respectively, can be determined
 and subsequently the individual pharmacokinetic profile of colchicine characterized (PMID
 24722393).

 CYP3A4 activity is given by the ratio of hydroxy-midazolam/midazolam assessed 2 hours after
 an oral administration of 1 mg midazolam (PMID 24722393).

 P-gp activity is given by the area under the curve (AUC) of a short kinetic that measures
 fexofenadine concentrations at 2, 3 and 6 hours after its oral administration of 120 mg (PMID
 24722393).

 These CYP3A4 and P-gp activities will be correlated with blood colchicine concentrations
 determined at different time points after an oral administration of 1.5 mg over 1 hour under
 fasting condition.

 The CYP3A4 and P-gp phenotyping will be proposed to all gouty patients who experienced gout
 flare and who fulfilled the inclusion and exclusion criteria.

 Participants will have 3 visits :

 -  V0: inclusion visit of patients who had untreated gout flare. Signed consent to the
 study will be collected and blood analysis performed. A blood collection and biobank of
 serum will be done using the blood harvested for gout care. Colchicine will be initiated
 at 1.5 mg over 1 hour (1 mg + 0.5 mg)

 -  V1: treatment efficiency will be assessed 48 h after V0 using Visual Analogue Scale
 (VAS) (0-100) pain measurement. Patients who will have an improvement of VAS more than
 50% of baseline VAS will be considered as responders to colchicine. In contrast an
 improvement less than 50% of baseline VAS will be considered as non-responders. Gout
 flare treatment will be adapted according to patient response. Colchicine treatment will
 be stopped after gout flare resolution

 -  V2: this visit will be appointed 1 month after V1 (far enough after resolution of gout
 flare). During this visit, the CYP3A4 and P-gp phenotyping will be performed. Patients
 will receive colchicine (1.5 mg over 1 hour) and midazolam (1 mg) and fexofenadine (120
 mg) orally. A kinetic of blood samples will be harvested with a total of 8 time points
 from T0 prior to drug administration to T6 6 hour post-drug administration. At the end
 of the phenotyping kinetic, urate-lowering therapy will be introduced according to usual
 care and dosage. This visit is the last visit of the protocol and patients will be
 followed-up as usual care.

 Plasma concentrations of colchicine, midazolam, hydroxymidazolam and fexofenadine will be
 quantified by liquid chromatography-tandem mass spectrometry (PMID 24295116).

 Plasma concentrations of colchicine will then correlate to CYP3A4 and P-gp activities
 estimated by midazolam and fexofenadine metabolism, respectively.

 The phenotyping will be performed in 34 colchicine responder and 34 colchicine non-responder
 patients.
Inclusion Criteria:

 Patients (> 18 years old) with gout flare defined by following items :

 -  Identification of sodium urate crystals in synovial fluid analysis

 -  Or gout flare diagnosis according to Nijmegen criteria (score > 8/13)

 -  Man (2 pts)

 -  History of flare (2 pts)

 -  Flare involving first metatarsophalangeal joint (2.5 pts)

 -  Maximum of flare within 24h (0.5pt),

 -  Redness (1 pt),

 -  History of hypertension or cardiovascular diseases (1.5 pts),

 -  Serum urate level > 360 µmol/l during flare (3.5 pts)

 -  Duration of flare < 48 h

 -  Monoarticular involvement

 Exclusion Criteria:

 -  Hypersensitivity to colchicine, fexofenadine, benzodiazepine or the excipients of
 these drugs

 -  Contra-indication to colchicine : chronic kidney disease stage 4-5, severe hepatic
 impairment, treatment by macrolide antibiotics

 -  Used of pain-killers other than acetaminophen

 -  Involvement in another clinical trial with drug administration

 -  Illiteracy

 -  Pregnant woman or breastfeeding