Binding of the D3-preferring antipsychotic candidate F17464 to dopamine D3 and D2 receptors: a PET study in healthy subjects with [11C]-(+)-PHNO

RATIONALE

F17464, a dopamine D3 receptor antagonist with relatively high D3 selectivity (70 fold vs D2 in vitro), exhibits an antipsychotic profile in preclinical studies, and therapeutic efficacy was demonstrated in a randomized placebo-controlled clinical trial in patients with schizophrenia (Bitter et al. Neuropsychopharmacology 44(11):1917-1924, 2019).

OBJECTIVE

This open-label study in healthy male subjects aimed at characterizing F17464 binding to D3/D2 receptors and the time course of receptor occupancy using positron emission tomography (PET) imaging with a D3-preferring tracer, [¹¹C]-(+)-PHNO.

METHODS

PET scans were performed at baseline and following a single 30 mg or 15 mg dose of F17464 (3 subjects/dose), and blood samples were collected for pharmacokinetic analysis. Receptor occupancy was calculated based upon reduction in binding potential of the tracer following F17464 administration. The relationship between plasma F17464 concentration and D3/D2 receptor occupancy was modeled and the plasma concentration corresponding to 50% receptor occupancy (EC₅₀) calculated.

RESULTS

Both doses of F17464 robustly blocked [¹¹C]-(+)-PHNO D3 receptor binding, with substantial occupancy from 1 h post-administration, which increased at 6-9 h (89-98% and 79-87% for the 30 mg and 15 mg groups, respectively) and remained detectable at 22 h. In contrast, D2 binding was only modestly blocked at all time points (< 18%). F17464 exhibited a combination of rapid peripheral kinetics and hysteresis (persistence of binding 22 h post-dose despite low plasma concentration). The best estimate of the EC₅₀ was 19 ng ml^-1 (~ 40 nM).

CONCLUSION

Overall, F17464 was strongly D3-selective in healthy volunteers, a unique profile for an antipsychotic candidate drug.

Randomized, double-blind, placebo-controlled study of F17464, a preferential D3 antagonist, in the treatment of acute exacerbation of schizophrenia

F17464, a highly potent preferential D3 antagonist, is a novel compound in development for schizophrenia treatment. This phase II, double-blind, randomized, placebo-controlled, parallel-group study in five European countries evaluated the efficacy and safety of F17464, 20 mg twice daily, versus placebo over 6 weeks in patients with acute exacerbation of schizophrenia. Change from baseline to Day 43 of the Positive and Negative Syndrome Scale (PANSS) total score was the primary outcome. The data from 134 randomized patients (67 per group) were analyzed (efficacy/safety). Using analysis of covariance (ANCOVA) after last observation carried forward (LOCF) imputation (primary analysis), the PANSS total score reduction was statistically significantly greater for F17464 than placebo treated subjects at endpoint (p = 0.014); using ANCOVA with Multiple Imputation (MI) method, the between-group difference was in favor of F17464 but did not reach statistical significance. Differences in PANSS positive and general psychopathology subscale score, Marder positive factor score, PANSS response, and PANSS resolution criteria were also statistically significant in favor of F17464 (p values < 0.05) using the LOCF method, with similar results as for the primary analysis using the MI method. Treatment-related adverse events (AEs) were reported in 49.3% and 46.3% of patients on F17464 and placebo, respectively. The most common AEs in F17464 group: insomnia, agitation, and increased triglycerides; worsening of schizophrenia/drug ineffective was less frequent in F17464. Interestingly, no weight gain, no extrapyramidal disorder except rare akathisia were observed under F17464. This 6-week trial demonstrated therapeutic efficacy of 40 mg/day F17464 in improving symptoms of acute exacerbation of schizophrenia with a favorable safety profile.

Propranolol pharmacokinetics in infants treated for Infantile Hemangiomas requiring systemic therapy: Modeling and dosing regimen recommendations

Propranolol has become the first choice therapy for complicated Infantile Hemangiomas (IH). The pharmacokinetics of propranolol were evaluated after repeated oral administration of a new pediatric solution of propranolol at 3 mg kg⁻¹ day⁻¹ given twice daily (BID) in infants (77‐243 days) with IH. A population model was built to describe the pharmacokinetics of propranolol in infants and to simulate different dosing regimens. One hundred and sixty‐seven plasma concentrations from 22 infants were used in the population analysis. Weight effect was tested on apparent clearance and volume of distribution. Monte‐Carlo simulations were performed for 4 dosing regimens: BID dosing with irregular or strict 12‐hour intervals and 2 different 3 time daily dosing (TID) regimens. The best model was a one‐compartment model with first‐order absorption and elimination rates. The weight affected the clearance but not the volume. Typical oral clearance was estimated at 3.06 L hour⁻¹ kg⁻¹ (95% CI: 1.14‐8.61 L hour⁻¹ kg⁻¹), close to adult clearance data. When regular BID dosing was compared to TID or irregular BID regimens, simulated median Cmin and Cmax were <20% different. To conclude, a model using a weight allometric function on clearance was established and confirmed that the dose in mg/kg should be used without adaptation by range of age in treatment of complicated IH. The simulations support the use of a BID dosing preferably to a TID dosing thanks to close Cmin and Cmax at steady state between both regimen and showed the possibility of irregular BID dosing, allowing early administration in the evening when needed.

Disposition and metabolism of [14C]-levomilnacipran, a serotonin and norepinephrine reuptake inhibitor, in humans, monkeys, and rats

Levomilnacipran is approved in the US for the treatment of major depressive disorder in adults. We characterized the metabolic profile of levomilnacipran in humans, monkeys, and rats after oral administration of [¹⁴C]-levomilnacipran. In vitro binding of levomilnacipran to human plasma proteins was also studied. Unchanged levomilnacipran was the major circulating compound after dosing in all species. Within 12 hours of dosing in humans, levomilnacipran accounted for 52.9% of total plasma radioactivity; the circulating metabolites N-desethyl levomilnacipran N-carbamoyl glucuronide, N-desethyl levomilnacipran, and levomilnacipran N-carbamoyl glucuronide accounted for 11.3%, 7.5%, and 5.6%, respectively. Similar results were seen in monkeys. N-Desethyl levomilnacipran and p-hydroxy levomilnacipran were the main circulating metabolites in rats. Mass balance results indicated that renal excretion was the major route of elimination with 58.4%, 35.5%, and 40.2% of total radioactivity being excreted as unchanged levomilnacipran in humans, monkeys, and rats, respectively. N-Desethyl levomilnacipran was detected in human, monkey, and rat urine (18.2%, 12.4%, and 7.9% of administered dose, respectively). Human and monkey urine contained measurable quantities of levomilnacipran glucuronide (3.8% and 4.1% of administered dose, respectively) and N-desethyl levomilnacipran glucuronide (3.2% and 2.3% of administered dose, respectively); these metabolites were not detected in rat urine. The metabolites p-hydroxy levomilnacipran and p-hydroxy levomilnacipran glucuronide were detected in human urine (≤1.2% of administered dose), and p-hydroxy levomilnacipran glucuronide was found in rat urine (4% of administered dose). None of the metabolites were pharmacologically active. Levomilnacipran was widely distributed with low plasma protein binding (22%).

Pharmacokinetics of Ferrous Sulphate (Tardyferon®) after Single Oral Dose Administration in Women with Iron Deficiency Anaemia

Iron-containing preparations available on the market vary in dosage, salt, and chemical state of iron contained in the preparation, as well as in the iron delivery process (immediate or prolonged-release). The present study aimed at characterizing the serum pharmacokinetics of iron in non pregnant women with iron deficiency anaemia (IDA) following a single oral administration of a prolonged-release ferrous sulphate tablet. This multicenter, single dose, open-label study was conducted in 30 women aged between 18 and 45 years with IDA. A single 160 mg oral dose of ferrous sulphate was given as 2 tablets of 80 mg of Tardyferon(®) under fasting conditions. Blood samples were collected before dosing and until 24 h post-dosing. Serum iron concentrations were determined using a routine colorimetric analytical method. Pharmacokinetic parameters were determined from the serum concentration profiles using a non compartmental approach. Serum profiles showed elevated levels of iron up to 12 h after drug intake. The median time to maximum serum concentrations (Tmax) occurred 4 h post-dosing. Between 2 and 8 h post-dosing, mean serum iron concentrations fluctuated by only 20%. Additionally, C8h and C12h represented on average 78.6% and 47.5% of the Cmax, respectively. This study demonstrates that a single oral dose of 160 mg Tardyferon(®) administered under fasting condition to 30 women with IDA leads to an optimal long-lasting release of iron in the gastrointestinal tract in the targeted population. This allows the attainment and maintenance of elevated serum iron levels for up to 12 h after administration.

[Intestinal B-mode sonography in patients with endemic sprue. Intestinal sonography in endemic sprue]

AIM

The value of ultrasonography in the diagnosis, follow-up and for the detection of complications in patients with celiac sprue has not yet been sufficiently evaluated. A pronounced back and forth motility with echo-rich hump reflexes in a fluid-filled small bowel with a reduction of Kerckring's plicae circulares and with a loss of their density and uniformity was empirically defined as a diagnostic sign of celiac sprue. In the present study, the sonographic signs of celiac sprue were examined as an indicator of active sprue.

METHOD

50 patients with histologically proven celiac sprue were examined with real time ultrasonography (3.5-7 MHz). The detection or exclusion of the defined sonographic signs of celiac sprue with intensified motility and reduction of Kerckring's plicae circulares with a loss of their density and uniformity were evaluated by two independent examiners and documented without knowledge of the clinical findings. The clinical activity (active vs. remission) was assessed according to clinical criteria (diarrhea, steatorrhea, weight loss). 38 healthy subjects and 50 patients with Crohn's disease served as controls.

RESULTS

In all 138 patients and controls adequate visualization of the bowel was achieved. In 16/50 (32%) patients with active celiac sprue changes of motility and reduction of Kerckring's plicae circulares with a loss of their density and uniformity were detected, whereas all 34/50 (68%) of patients with celiac sprue in remission did not have this pattern. In none of the controls with Crohn's disease or in the healthy subjects comparative sonographic signs of active celiac sprue were observed. In four patients with active celiac sprue a circumscript echopoor tumor of the small bowel wall could be sonographically detected, which turned out to be T-cell lymphoma in three and a carcinoma of the small intestine in one patient. An increased number of and/or enlarged mesenteric lymph nodes were found in patients with active celiac sprue.

CONCLUSION

Changes of motility and reduction of Kerckring's plicae circulares with loss of density and uniformity at ultrasonography are a reliable indicator of active celiac sprue.

[Intestinal ultrasound in rare small and large intestinal diseases]

Intestinal ultrasonography is a meanwhile established and valid diagnostic method in inflammatory bowel disease, diverticulitis, and appendicitis. Little, however, is known about other more rare intestinal diseases. Serving as a tertiary referral center for a broad spectrum of intestinal diseases we therefore report some aspects of ultrasonography in patients with acute and chronic enteritis and colitis of different origin, e.g., bacterial and viral colitis, ileocecal tuberculosis, AIDS-related enteritis, neutropenic colitis, cystic fibrosis, celiac sprue, vasculitis, benign and malignant tumors of the intestine, amyloidosis, ischemic colitis, and radiogenic enteritis. Ultrasonography may display the transformation of the intestinal wall from normal to pathological states both in inflammatory and neoplastic disease. Besides demonstrating the transmural aspect of inflammation it also shows the mesenteric reaction as well as complications such as fistula, abscesses, stenosis, or ileus. Furthermore, in some diseases intestinal ultrasonography may serve as a diagnostic clue if typical patterns of the bowel wall and impaired peristalsis can be demonstrated. This may lead to an important reduction of invasive and expensive procedures. Ultrasonography is of definite help in the follow-up of inflammatory changes of the bowel wall and primarily diagnostic with respect of other entities (e.g., penicillin-induced segmental hemorrhagic colitis). A sonographic differential diagnosis of diseases of the bowel wall on a purely morphological basis, however, is difficult and rather the exception than the rule. The information gained by ultrasonography regarding intestinal disease, however, is as important and valid as e.g., in case of focal lesions of the liver.

Prediction of carboplatin clearance from standard morphological and biological patient characteristics

BACKGROUND

Hematologic toxicity of an antineoplastic drug, carboplatin, is largely dependent on its pharmacokinetics. Its therapeutic efficacy may be related to plasma drug exposure. Dosage adjustment based on isotopic determination of glomerular filtration rate has been proposed, but its ambulatory use is not yet conceivable. The dosage adjustment based on a patient's creatinine clearance relies on accurate measurement of urine volume per unit time and can be done with ease.

PURPOSE

A population pharmacokinetics study was undertaken to determine a relationship between carboplatin clearance and patient characteristics. A predictive formula was derived that was then prospectively evaluated, and its outcome was compared with that obtained by other methods available to predict carboplatin clearance.

METHODS

Plasma carboplatin pharmacokinetics determined as ultrafilterable platinum in 70 patients (age range, 23-84 years) treated with different combination regimens that included carboplatin at doses ranging from 184 mg to 950 mg (1-hour intravenous infusion) for various tumor types. Data were analyzed using the nonlinear mixed effects model (NONMEM). The data from 34 patients (46 cycles) were utilized to derive the most predictive formula. The reliability of the formula was subsequently evaluated by analyzing the data obtained from 36 other patients (49 cycles).

RESULTS

Carboplatin clearance (mL/min) was found to be best predicted by the following formula: 0.134.weight + [218.weight.(1-0.00457.age).(1-0.314.sex)]creatinine expressed in micromolar concentration (with weight in kg, age in years, and sex = 0 if male and sex = 1 if female). Prospectively, this formula predicted the carboplatin clearance with good precision (median absolute percent error of 10% [range, 0% to 30%]) and minimal bias (median percent error of 2% [range, -25% to 30%]). This method of prediction was as accurate as the one derived from the measurement of glomerular filtration rate following the injection of 51 chromium-EDTA.

CONCLUSION

This formula for the determination of carboplatin clearance can permit individualized determination of carboplatin dosage in adults by simply multiplying the calculated carboplatin clearance by the area under the curve for the desired dosage administration.

A pharmacologically guided phase I study of carboplatin in combination with methotrexate and vinblastine in advanced urothelial cancer

Carboplatin is an alternative for cisplatin in the treatment of urothelial cancers. A pharmacologically guided phase I study of carboplatin in combination with methotrexate (30 mg/m2) and vinblastine (4 mg/m2) was conducted in ten patients by increment of the area under the plasma concentration versus time curve (AUC) for ultrafilterable carboplatin using the Calvert formula. The maximal tolerated AUC was 5 mg ml-1 min, with neutropenia being the dose-limiting toxicity. There was a significant linear correlation between the percentage of decrease in neutrophil count and the carboplatin AUC. Determination of the glomerular filtration rate by the isotopic method allowed us to adapt the dose of carboplatin given to patients suffering from urothelial cancer, who frequently have impaired renal function. The recommended AUC for phase II study is 4 mg ml-1 min.

[The effect of oral butyl-biguanide on oral glucose tolerance and renal glucose reabsorption in normal human subjects in vivo (author's transl)]

1. Oral glucose tolerance in 11 normal subjects was significantly improved after peroral administration of 150 mg of butyl-biguanide. 2. On the other hand maxiumum capacity of renal glucose reabsorption (TmG) and lowest glomerular glucose filtration rate at which glucosuria was recorded (F min) remained uninfluenced after 150 mg of butyl-biguanide in 7 normal subjects. 3. These results are compatible with the hypothesis that the oral administration of therapeutic doses of biguanides yields concentrations at the luminal face of the intestine which inhibit glucose resorption. Plasma concentrations following oral intake of the same dose of biguanide are too low to exert any inhibiting action on renal glucose reabsorption as demonstrated by the present in vivo studies. 4. Urinary flow rate and inulin clearance remained unaltered after butyl-biguanide in these normal subjects.