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.

Cutaneous neurofibromas: patients' medical burden, current management and therapeutic expectations: results from an online European patient community survey.

BACKGROUND: Neurofibromatosis type 1 is an inherited condition with variable phenotypic expression and a high medical and social burden. The objectives of this patient survey were to better understand the real-world experiences of patients living with cutaneous neurofibromas (cNF), to perceive their satisfaction and feelings about cNF current management (only laser and surgery are currently available), and to highlight their expectations of new therapeutic modalities. RESULTS: One hundred seventy patients from 4 European countries took part in the study, 65% (n = 110) were women and mean age was 39 years old. 96% (n = 164) of respondents have cNF on visible parts of the body and the survey confirmed that total number of cNF and visibility increase with age. Patients reported that cNF mainly impacts everyday mood, general daily life and social life. The visibility of cNF had a higher impact than their number. 92% (n = 156) of patients have a regular and multidisciplinary medical follow-up. The dermatologist is one of the most consulted healthcare professionals. 76% (n = 130) of respondents have treated their cNF: 65% (n = 111) had surgery and 38% (n = 64) had multiple laser sessions. Frequency of operations and regrowth of cNF were the two most unsatisfactory aspects with both treatments for patients. Indeed, after removal, new cNF appear in more than 75% (n = 128) of cases. As a future treatment, patients expected a topical (30%, n = 51) or oral medication (29%, n = 50). Around 2 out of 3 patients would agree to take it at least once a day or more for life but they would like a well-tolerated treatment. According to patients, the most important effectiveness criteria of a new treatment are to block cNF growth and reduce their number. 70% (n = 119) of patients would consider a future treatment moderately effective to very effective if it could clear 30% of cNF. CONCLUSIONS: This first cNF European patient community survey confirmed that the visible stigma and unaesthetic aspect of cNF have an important impact on patients' quality of life. The survey highlighted that patients were not entirely satisfied with the actual surgery and laser treatments and revealed their clear and realistic expectations for future treatment of cNF.