Drug repurposing: Misconceptions, challenges, and opportunities for academic researchers.

Drug repurposing is promoted as a cost- and time-effective mechanism for providing new medicines. Often, however, there is insufficient consideration by academic researchers of the processes required to ensure that a repurposed drug can be used for a new indication. This may explain the inability of drug repurposing to fulfill its promise. Important aspects, often overlooked, include financial and intellectual property considerations, the clinical and regulatory path, and clinical equipoise, which provides ethical justification for randomized controlled trials. The goal of drug repurposing is to obtain a new regulator-approved label for an existing drug, and so, the trajectory for drug repurposing and traditional drug development is similar. Here, we discuss factors critical for a successful repurposed medicine to help academic investigators better identify drug repurposing opportunities.

The mixed anion mineral parnauite Cu9[(OH)10|SO4|(AsO4)2]·7H2O--a Raman spectroscopic study.

The mixed anion mineral parnauite Cu(9)[(OH)(10)|SO(4)|(AsO(4))(2)]·7H(2)O from two localities namely Cap Garonne Mine, Le Pradet, France and Majuba Hill mine, Pershing County, Nevada, USA has been studied by Raman spectroscopy. The Raman spectrum of the French sample is dominated by an intense band at 975 cm(-1) assigned to the ν(1) (SO(4))(2-) symmetric stretching mode and Raman bands at 1077 and 1097 cm(-1) may be attributed to the ν(3) (SO(4))(2-) antisymmetric stretching mode. Two Raman bands 1107 and 1126 cm(-1) are assigned to carbonate CO(3)(2-) symmetric stretching bands and confirms the presence of carbonate in the structure of parnauite. The comparatively sharp band for the Pershing County mineral at 976 cm(-1) is assigned to the ν(1) (SO(4))(2-) symmetric stretching mode and a broad spectral profile centered upon 1097 cm(-1) is attributed to the ν(3) (SO(4))(2-) antisymmetric stretching mode. Two intense bands for the Pershing County mineral at 851 and 810 cm(-1) are assigned to the ν(1) (AsO(4))(3-) symmetric stretching and ν(3) (AsO(4))(3-) antisymmetric stretching modes. Two Raman bands for the French mineral observed at 725 and 777 cm(-1) are attributed to the ν(3) (AsO(4))(3-) antisymmetric stretching mode. For the French mineral, a low intensity Raman band is observed at 869 cm(-1) and is assigned to the ν(1) (AsO(4))(3-) symmetric stretching vibration. Chemical composition of parnauite remains open and the question may be raised is parnauite a solid solution of two or more minerals such as a copper hydroxy-arsenate and a copper hydroxy sulphate.

Structure of selected basic zinc/copper (II) phosphate minerals based upon near-infrared spectroscopy--implications for hydrogen bonding.

The NIR spectra of reichenbachite, scholzite and parascholzite have been studied at 298 K. The spectra of the minerals are different, in line with composition and crystal structural variations. Cation substitution effects are significant in their electronic spectra and three distinctly different electronic transition bands are observed in the near-infrared spectra at high wavenumbers in the 12,000-7600 cm(-1) spectral region. Reichenbachite electronic spectrum is characterised by Cu(II) transition bands at 9755 and 7520 cm(-1). A broad spectral feature observed for ferrous ion in the 12,000-9000 cm(-1) region both in scholzite and parascholzite. Some what similarities in the vibrational spectra of the three phosphate minerals are observed particularly in the OH stretching region. The observation of strong band at 5090 cm(-1) indicates strong hydrogen bonding in the structure of the dimorphs, scholzite and parascholzite. The three phosphates exhibit overlapping bands in the 4800-4000 cm(-1) region resulting from the combinations of vibrational modes of (PO(4))(3-) units.

Raman spectroscopic study of a hydroxy-arsenate mineral containing bismuth-atelestite Bi2O(OH)(AsO4).

The Raman spectrum of atelestite Bi2O(OH)(AsO4), a hydroxy-arsenate mineral containing bismuth, has been studied in terms of spectra-structure relations. The studied spectrum is compared with the Raman spectrum of atelestite downloaded from the RRUFF database. The sharp intense band at 834 cm(-1) is assigned to the ν1 AsO4(3-) (A1) symmetric stretching mode and the three bands at 767, 782 and 802 cm(-1) to the ν3 AsO4(3-) antisymmetric stretching modes. The bands at 310, 324, 353, 370, 395, 450, 480 and 623 cm(-1) are assigned to the corresponding ν4 and ν2 bending modes and BiOBi (vibration of bridging oxygen) and BiO (vibration of non-bridging oxygen) stretching vibrations. Lattice modes are observed at 172, 199 and 218 cm(-1). A broad low intensity band at 3095 cm(-1) is attributed to the hydrogen bonded OH units in the atelestite structure. A weak band at 1082 cm(-1) is assigned to δ(BiOH) vibration.

Spectroscopy of selected copper group minerals: Chalcophyllite and chenevixite-implications for hydrogen bonding.

NIR and IR spectroscopy has been applied for detection of chemical species and the nature of hydrogen bonding in arsenate complexes. The structure and spectral properties of copper(II) arsenate minerals: chalcophyllite and chenevixite are compared with copper(II) sulphate minerals: devilline, chalcoalumite and caledonite. Split NIR bands in the electronic spectrum of two ranges 11,700-8500 cm(-1) and 8500-7200 m(-1) confirm distortion of octahedral symmetry for Cu(II) in the arsenate complexes. The observed bands with maxima at 9860 and 7750 cm(-1) are assigned to Cu(II) transitions (2)B(1g)-->(2)B(2g) and (2)B(1g)-->(2)A(1g). Overlapping bands in the NIR region 4500-4000 cm(-1) is the effect of multi-anions OH(-), (AsO(4))(3-) and (SO(4))(2-). The observation of broad and diffuse bands in the range 3700-2900 cm(-1) confirms strong hydrogen bonding in chalcophyllite relative to chenevixite. The position of the water bending vibrations indicates the water is strongly hydrogen bonded in the mineral structure. The strong absorption feature centred at 1644 cm(-1) in chalcophyllite indicates water is strongly hydrogen bonded in the mineral structure. The H(2)O-bending vibrations shift to low wavenumbers in chenevixite and an additional band observed at 1390 cm(-1) is related to carbonate impurity. The characterisation of IR spectra by nu(3) antisymmetric stretching vibrations of (SO(4))(2-) and (AsO(4))(3) ions near 1100 and 800 cm(-1) respectively is the result of isomorphic substitution for arsenate by sulphate in both the minerals of chalcophyllite and chenevixite.

A Raman spectroscopic study of the antimonite mineral peretaite Ca(SbO)(4)(OH)(2)(SO(4))(2).2H(2)O.

Raman spectra of mineral peretaite Ca(SbO)(4)(OH)(2)(SO(4))(2).2H(2)O were studied, and related to the structure of the mineral. Raman bands observed at 978 and 980cm(-1) and a series of overlapping bands observed at 1060, 1092, 1115, 1142 and 1152cm(-1) are assigned to the SO(4)(2-)nu(1) symmetric and nu(3) antisymmetric stretching modes. Raman bands at 589 and 595cm(-1) are attributed to the SbO symmetric stretching vibrations. The low intensity Raman bands at 650 and 710cm(-1) may be attributed to SbO antisymmetric stretching modes. Raman bands at 610cm(-1) and at 417, 434 and 482cm(-1) are assigned to the SO(4)(2-)nu(4) and nu(2) bending modes, respectively. Raman bands at 337 and 373cm(-1) are assigned to O-Sb-O bending modes. Multiple Raman bands for both SO(4)(2-) and SbO stretching vibrations support the concept of the non-equivalence of these units in the peretaite structure.

Raman spectroscopic study of the tellurite mineral: rodalquilarite H3Fe2(3+)(Te4+O3)4Cl.

Tellurites may be subdivided according to formula and structure. There are five groups based upon the formulae (a) A(XO3); (b) A(XO3).xH2O; (c) A2(XO3)3.xH2O; (d) A2(X2O5) and (e) A(X3O8). Rodalquilarite, a tellurite mineral of type (a) has been studied using Raman spectroscopy. Observed from the spectra was the presence of protons, an essential stabilising element for the minerals structure and stability. The tellurite ion should show a maximum of six bands. The free tellurite ion shows C3v symmetry and has four modes, 2A1 and 2E. Three Raman bands at 726, 755 and 780 cm(-1) are assigned to the nu1 (TeO3)2- symmetric stretching mode and the two bands at 610 and 642 cm(-1) are attributed to the nu3 (TeO3)2- antisymmetric stretching mode. The two bands at 321 and 345 cm(-1) and the two bands at 449 and 473 cm(-1) are assigned to the (TeO3)2-nu2 (A1) bending mode and (TeO3)2-nu4 (E) bending mode. Raman bands observed at 2341, 2796 and 2870 cm(-1) are attributed to OH stretching vibrations caused by interaction between the protons and the oxygen of the tellurite units. The values for these OH stretching vibrations provide hydrogen bond distances of 2.550 (6) A (2341 cm(-1)), 2.610 (3) A (2796 cm(-1)) and 2.623 (2) A (2870 cm(-1)) which are comparatively short for secondary minerals.

Raman spectroscopic study of the tellurite minerals: carlfriesite and spiroffite.

Raman spectroscopy has been used to study the tellurite minerals spiroffite and carlfriesite, which are minerals of formula type A(2)(X(3)O(8)) where A is Ca(2+) for the mineral carlfriesite and is Zn(2+) and Mn(2+) for the mineral spiroffite. Raman bands for spiroffite observed at 721 and 743 cm(-1), and 650 cm(-1) are attributed to the nu(1) (Te(3)O(8))(2-) symmetric stretching mode and the nu(3) (Te(3)O(8))(2-) antisymmetric stretching modes, respectively. A second spiroffite mineral sample provided a Raman spectrum with bands at 727 cm(-1) assigned to the nu(1) (Te(3)O(8))(2-) symmetric stretching modes and the band at 640cm(-1) accounted for by the nu(3) (Te(3)O(8))(2-) antisymmetric stretching mode. The Raman spectrum of carlfriesite showed an intense band at 721 cm(-1). Raman bands for spiroffite, observed at (346, 394) and 466 cm(-1) are assigned to the (Te(3)O(8))(2-)nu(2) (A(1)) bending mode and nu(4) (E) bending modes. The Raman spectroscopy of the minerals carlfriesite and spiroffite are difficult because of the presence of impurities and other diagenetically related tellurite minerals.

Raman spectroscopic study of the tellurite minerals: rajite and denningite.

Tellurites may be subdivided according to formula and structure. There are five groups based upon the formulae (a) A(XO3), (b) A(XO3).xH2O, (c) A2(XO3)3.xH2O, (d) A2(X2O5) and (e) A(X3O8). Raman spectroscopy has been used to study rajite and denningite, examples of group (d). Minerals of the tellurite group are porous zeolite-like materials. Raman bands for rajite observed at 740, and 676 and 667 cm(-1) are attributed to the nu1 (Te2O5)(2-) symmetric stretching mode and the nu3 (TeO3)(2-) antisymmetric stretching modes, respectively. A second rajite mineral sample provided a more complex Raman spectrum with Raman bands at 754 and 731 cm(-1) assigned to the nu1 (Te2O5)(2-) symmetric stretching modes and two bands at 652 and 603 cm(-1) are accounted for by the nu3 (Te2O5)(2-) antisymmetric stretching mode. The Raman spectrum of dennigite displays an intense band at 734 cm(-1) attributed to the nu1 (Te2O5)(2-) symmetric stretching mode with a second Raman band at 674 cm(-1) assigned to the nu3 (Te2O5)(2-) antisymmetric stretching mode. Raman bands for rajite, observed at (346, 370) and 438 cm(-1) are assigned to the (Te2O5)(2-)nu2 (A1) bending mode and nu4 (E) bending modes.