Thermal and Structural Characterization of Two Crystalline Polymorphs of Tafamidis Free Acid

Tafamidis, chemical formula C14H7Cl2NO3, is a drug used to delay disease progression in adults suffering from transthyretin amyloidosis, and is marketed worldwide under different tradenames as a free acid or in the form of its meglumine salt. The free acid (CAS no. 594839-88-0) is reported to crystallize as distinct (polymorphic) crystal forms, the thermal stability and structural features of which remained thus far undisclosed. In this paper, we present-by selectively isolating highly pure batches of Tafamidis Form 1 and Tafamidis Form 4-the full characterization of these solids, in terms of crystal structures (determined using state-of-the-art structural powder diffraction methods) and spectroscopic and thermal properties. Beyond conventional thermogravimetric and calorimetric analyses, variable-temperature X-ray diffraction was employed to measure the highly anisotropic response of these (poly)crystalline materials to thermal stimuli and enabled the determination of the linear and volumetric thermal expansion coefficients and of the related indicatrix. Both crystal phases are monoclinic and contain substantially flat and π-π stacked Tafamidis molecules, arranged as centrosymmetric dimers by strong O-H···O bonds; weaker C-H···N contacts give rise, in both polymorphs, to infinite ribbons, which guarantee the substantial stiffness of the crystals in the direction of their elongation. Complete knowledge of the structural models will foster the usage of full-pattern quantitative phase analyses of Tafamidis in drug and polymorphic mixtures, an important aspect in both the forensic and the industrial sectors.

Preparation and Solid-State Characterization of Eltrombopag Crystal Phases

Eltrombopag, of C₂₅H₂₂N₄O₄ chemical formula, is a drug used against thrombocytopenia, marketed worldwide under different tradenames in the form of its bis-olamine salt. The free acid (CAS no. 496775-61-2) is an intermediate species used for the final drug isolation and is reported to crystallize in more than 20 distinct crystal forms, including a large number of hydrates and solvates. Their identification, and, ultimately, their quantification in industrial lots require the usage of accurately measured X-ray powder diffraction pattern, as well as the assessment of the metrical features (crystal symmetry and lattice parameters), nowadays accessible by powerful crystallographic software. Here, the complete indexing of 13 monophasic samples, prepared using literature or newly tailored crystallization methods, jointly to simultaneous thermogravimetric and calorimetric analyses and to variable temperature X-ray diffraction studies, provide a clear picture of the stability fields of the different crystal phases and their mutual interconversion processes, leading, in a few cases, to new and unexpected crystalline polymorphs or solvates of the pristine unsolvated Form I.

Slab narrowing in the Central Mediterranean: the Calabro-Ionian subduction zone as imaged by high resolution seismic tomography

A detailed 3D image of the Calabro-Ionian subduction system in the central Mediterranean was obtained by means of a seismic tomography, exploiting a large dataset of local earthquakes and computing algorithms able to build a dense grid of measure nodes. Results show that the slab is continuous below the southern sector of the Calabro-Peloritan Arc, but the deformation processes developing at its edges are leading to its progressive narrowing, influencing tectonics and magmatism at the surface, and with possible stress concentration in the tip zones. In the southwest, the deformation occurring at a free slab edge lead to propagation of a vertical lithospheric tear in the overriding plate, which extends along a NW-SE fault system (Aeolian-Tindari-Letojanni) up to about 30 km into the Ionian Sea; further southeast, the lithosphere appears only flexed and not broken yet. In the northeast, the slab seems to break progressively, parallel to the trench. Finally, northwest of Mt. Etna, the tomography highlights low V_P that can be related to an upwelling of deep mantle material likely flowing laterally through a window opened by the complete slab detachment.

In vitro effects of novel glycopeptide antibiotics on the reactivity of the lipopolysaccharide (LPS) of S. minnesota R595

Four novel glycopeptide antibiotics, namely MDL 62708, MDL 63155, MDL 62827, MDL 62873 (mideplanin), plus teicoplanin, which differ in their chemical structure, were used to examine the relationship between the structure of glycopeptides and their LPS neutralization activity. Compound MDL 62708 (100 micrograms/ml) significantly reduced (P < 0.01 vs. antibiotic-free LPS, by Fisher's PLSD Test) metachromatic reactivity of S. minnesota R595 LPS (500 micrograms/ml) as evaluated by the DMB test. The remaining glycopeptides showed a significant reduction of the metachromatic reactivity, although at concentrations (333 and 1000 micrograms/ml) higher than MDL 62708. Data obtained with LAL test appeared in accordance with those of the other techniques: all the glycopeptides used (100 and 1000 micrograms/ml) significantly (P < 0.05) reduced the reactivity of S. minnesota R595 LPS (50 pg/ml), and the lowest concentration of MDL 62708 (10 pg/ml) used produced a substantial, although not significant, reduction of the LPS reactivity with LAL. The antibiotic/LPS ratios associated to a significant reduction of LPS reactivity were 3.3/5 (wt/wt) and 2/1 (wt/wt) for DMB and LAL tests respectively. Such ratio appeared to be even lower for MDL 62708. In conclusion, the four new glycopeptides, when tested at an antibiotic/LPS ratio about 1000 times lower than that which can be found in vivo, were able to reduce the reactivity of LPS in the in vitro models used. Teicoplanin aglycone MDL 62708, which also lacks the teicoplanin fatty acid, seems to have the same anti-LPS activity as the parental antibiotic, thus suggesting an important role for the glycopeptide backbone and NH2 groups in LPS-neutralizing effect.