RESUMEN
The prediction of solubilities of compounds by means of molecular simulation has been receiving increasing attention due to the key role played by solubility in countless applications. We have predicted the aqueous solubility of urea at 300 K from chemical potential calculations for two urea model combinations: Özpinar/TIP3P and Hölzl/(TIP4P/2005). The methodology assumes that the intramolecular contribution of the urea molecule to the chemical potentials is identical in the crystal and in solution and, hence, cancels out. In parallel to the chemical potential calculations, we also performed direct coexistence simulations of a urea crystal slab in contact with urea-water solutions with the aim to identify upper and lower bounds to the solubility value using an independent route. The chemical potential approach yielded similar solubilities for both urea models, despite the actual chemical potential values showing a significant dependence on the force field. The predicted solubilities for the two models were 0.013-0.018 (Özpinar) and 0.008-0.012 (Hölzl) mole fraction, which are an order of magnitude lower than the experimental solubility that lies in a range of 0.125-0.216 mole fraction. The direct coexistence solubility bounds were relatively wide and did not encompass the chemical potential based solubilities, although the latter were close to the lower bound values.
RESUMEN
BACKGROUND: PrabotulinumtoxinA is a 900-kDa botulinum toxin type A produced by Clostridium botulinum. OBJECTIVES: The authors sought to investigate the efficacy and safety of prabotulinumtoxinA compared to onabotulinumtoxinA and placebo for the treatment of glabellar lines. METHODS: This was a 150-day, multicenter, double-blind, controlled, single-dose Phase III study. Adult patients (n = 540) with moderate to severe glabellar lines at maximum frown as assessed by the investigator on the validated 4-point Glabellar Line Scale (0 = no lines, 1 = mild, 2 = moderate, 3 = severe), who also felt that their glabellar lines had an important psychological impact, were enrolled. Patients were randomized 5:5:1 to receive a single treatment (0.1 mL injected into each of 5 glabellar sites) of 20 U prabotulinumtoxinA (n = 245), 20 U onabotulinumtoxinA (n = 246), or placebo (n = 49). The primary efficacy endpoint was the proportion of responders (patients with a Glabellar Line Scale score of 0 or 1 at maximum frown by investigator assessment) on day 30. RESULTS: Responder rates for the primary efficacy endpoint were 87.2%, 82.8%, and 4.2% in the prabotulinumtoxinA, onabotulinumtoxinA, and placebo groups, respectively. The absolute difference between prabotulinumtoxinA and onabotulinumtoxinA groups was 4.4% (95% confidence interval [-1.9, 10.8]). Given that the lower bound of the 95% confidence interval for the difference was less than -10.0%, noninferiority of prabotulinumtoxinA vs onabotulinumtoxinA was concluded. Five patients (3 prabotulinumtoxinA, 1.2%; 1 onabotulinumtoxinA, 0.4%; 1 placebo, 2.0%) experienced serious adverse events, none of which were study drug related. CONCLUSIONS: A single treatment of 20 U prabotulinumtoxinA was safe and effective and noninferior to 20 U onabotulinumtoxinA for the treatment of moderate to severe glabellar lines.