An example of how to handle amorphous fractions in API during early pharmaceutical development: SAR114137--a successful approach.

The so-called pharmaceutical solid chain, which encompasses drug substance micronisation to the final tablet production, at pilot plant scale is presented as a case study for a novel, highly potent, pharmaceutical compound: SAR114137. Various solid-state analytical methods, such as solid-state Nuclear Magnetic Resonance (ssNMR), Differential Scanning Calorimetry (DSC), Dynamic Water Vapour Sorption Gravimetry (DWVSG), hot-stage Raman spectroscopy and X-ray Powder Diffraction (XRPD) were applied and evaluated to characterise and quantify amorphous content during the course of the physical treatment of crystalline active pharmaceutical ingredient (API). DSC was successfully used to monitor the changes in amorphous content during micronisation of the API, as well as during stability studies. (19)F solid-state NMR was found to be the method of choice for the detection and quantification of low levels of amorphous API, even in the final drug product (DP), since compaction during tablet manufacture was identified as a further source for the formation of amorphous API. The application of different jet milling techniques was a critical factor with respect to amorphous content formation. In the present case, the change from spiral jet milling to loop jet milling led to a decrease in amorphous API content from 20-30 w/w% to nearly 0 w/w% respectively. The use of loop jet milling also improved the processability of the API. Stability investigations on both the milled API and the DP showed a marked tendency for recrystallisation of the amorphous API content on exposure to elevated levels of relative humidity. No significant impact of amorphous API on either the chemical stability or the dissolution rate of the API in drug formulation was observed. Therefore, the presence of amorphous content in the oral formulation was of no consequence for the clinical trial phases I and II.

From laboratory to pilot plant: the solid-state process development of a highly potent cathepsin S/K inhibitor.

The solid-state development for the low dose drug molecule SAR114137, a selective and reversible inhibitor of cysteine cathepsin S/K, is reported. Six polymorphic forms as well as various solvate phases were discovered by an extensive polymorphism screening. The solid phase characterizations revealed that phase 1, from which a single crystal structure could be obtained, is the thermodynamically most stable form and therefore it was chosen for pharmaceutical development. The successful scale-up from development laboratory into pilot plant for the crystallization and drying processes is presented. Testing of different drying techniques, like agitated drying in conical or filter dryers as well as spray drying, proved them to be very promising alternatives to the conventional tray drying process and might be used during the industrialization phase of the project. The use of online analytical tools (e.g., Raman spectroscopy) for a better process understanding and as tools for process optimization is shown. Furthermore, wet milling by ultrasound was performed on laboratory scale and discussed as potential option to reach the desired particle size distribution necessary for a good content uniformity of the API in an oral formulation.

Challenges in the development of hydrate phases as active pharmaceutical ingredients--an example.

The challenges during pilot plant scale-up of the SAR474832 API (active pharmaceutical ingredient) production in view of crystallization, isolation, drying and micronization are reported. A variety of different solid-state analytical and spectroscopic techniques (also coupled methods) were applied in order to understand the complex phase transition behaviour of the crystallographic phase (form 1) chosen for development: a partially non-stoichiometric channel-hydrate (x (1+1.25) H(2)O) crystallizing from pure water in the crystal habit of fine needles, which tend to agglomerate upon isolation and drying. Processes have been developed for drying, sieving and micronization by jetmilling to avoid non-desired phase transitions (overdrying effects) into other hydrate forms. Special methods have been established to minimize, monitor and control the formation of amorphous content during the particle size reduction steps. By optimizing all production parameters it was possible to produce API batches in 10 kg scale with physical quality suitable for oral formulations (e.g. particle size d 90 value<20 µm, water content and crystallographic phase corresponding to desired form 1 of SAR474832).

New technology for the investigation of water vapor sorption-induced crystallographic form transformations of chemical compounds: a water vapor sorption gravimetry-dispersive Raman spectroscopy coupling.

In this study, a new dynamic water vapor sorption gravimetry (DWVSG)-Raman spectroscopy coupled system is presented and described for the investigation of water (de)sorption-induced solid-phase transition of active pharmaceutical ingredients (APIs). The innovative characteristic of the system is the possibility to measure up to 23 samples gravimetrically and spectroscopically in one sorption/desorption experiment. The used dispersive RXN1 Raman system with a 6-mm laser spot P(h) AT probe head is ideal for this kind of coupled technology, as the energy density at the point of measurement of the sample is low, which grants that gravimetrical data and the state of the sample (phase transformations or even degradation) are not influenced by the laser beam. The capabilities of the system were tested by the investigation of a crystalline, nonstoichiometric hydrate form (form 1) and the corresponding X-ray amorphous form of an API (SAR474832). For the crystalline hydrate form, it was possible to correlate the weight loss at low humidities to a crystallographic phase transition (form 2). Furthermore, it was possible to show that the phase transition is reversible upon water uptake (sorption cycle); however, a further intermediate crystal form (form 3) is involved in the rehydration process. By multivariate curve resolution analysis of the Raman spectra, the form distribution diagrams of the desorption/sorption cycle could be constructed. For the amorphous material, the recrystallization process was monitored by the changes in the Raman spectra. The recrystallization point was detected at high humidities (>90% relative humidity), the crystal phase formed was identified (form 1), and the time needed for the conversion into the crystalline state was determined. The form transformation processes were visualized by contour plots (time/humidity vs. wavenumber vs. Raman intensity). In summary, it was concluded that the presented water sorption gravimetry-Raman spectroscopy coupling is a powerful tool to study solid-state transitions of pharmaceutical compounds or galenic formulations. The information obtained can, for example, be used to optimize drying, conditioning, or rerystallization processes of chemical products or to determine their optimal storage conditions. This is especially interesting for physically and chemically labile hydrate phases.

Spiro(imidazo[1,2-a]pyrano[2,3-c]pyridine-9-indenes) as inhibitors of gastric acid secretion.

Asymmetric and symmetric spiro(imidazo[1,2-a]pyrano[2,3-c]pyridine-9-indenes) were prepared using a synthetic approach that comprised a cross-metathesis reaction and an acid-catalyzed cycloisomerisation as key steps. The target compounds constitute potent inhibitors of the gastric proton pump enzyme with inhibitory activity comparable to potassium-competitive acid blockers (P-CABs) belonging to the known 9-aryl-7H-8,9-dihydropyrano[2,3-c]imidazo[1,2-a]pyridine series. Spiro(imidazo[1,2-a]pyrano[2,3-c]pyridine-9,2'-indenes) represent the first example for P-CABs, in which the distance between the heterocyclic scaffold and the aryl residue has been modified, and are promising candidates for further development as anti-ulcer drugs.

Physicochemical, crystallographic, thermal, and spectroscopic behavior of crystalline and X-ray amorphous ciclesonide.

Single crystal structure experiments revealed that the orthorhombic needles of Ciclesonide crystallized in P2(1)2(1)2(1) space group with four independent molecules in the unit cell. Amorphous Ciclesonide was prepared by lyophilization and characterized in comparison with crystalline material by differential scanning calorimetry (DSC), Fourier transformed (FT)-Raman spectroscopy, powder X-ray diffraction, dissolution, and saturation solubility experiments. Significant differences in the dissolution, thermal, and spectrometric behavior were observed for both solid-state phases. DSC- and FT-Raman methods for the determination of amorphous content in crystalline Ciclesonide samples were established. Isothermal and dynamical recrystallization studies on amorphous Ciclesonide were conducted using dispersive hot-stage Raman microscopy. The recrystallization was observed to be a two-step process with an induction period (most likely nuclei formation) followed by the actual recrystallization (crystal growth). The recrystallization rate constants and Avrami exponents (n = 2) were determined from the isothermal experiments at various temperatures using Johnson-Mehl-Avrami theory. Isothermal activation energies were obtained from Arrhenius plots using the temperature dependence of (a) the rate constants (160.4 kJ/mol) and (b) the induction time (140.9 kJ/mol) of the isothermal hot-stage experiments.

5-Substituted 1H-pyrrolo[3,2-b]pyridines as inhibitors of gastric acid secretion.

A series of novel 1H-pyrrolo[3,2-b]pyridines was prepared relying on a copper iodide catalyzed cyclization of 2-prop-1-ynylpyridin-3-amines. A structure-activity relationship was established focusing on the influence of the substitution pattern in position 1, 3, and 5 of the heterocycle on anti-secretory activity, lipophilicity, and pK(a) value. Some of the compounds proved to be potent inhibitors of the gastric acid pump.

Synthesis and evaluation of 7H-8,9-dihydropyrano[2,3-c]imidazo[1,2-a]pyridines as potassium-competitive acid blockers.

7H-8,9-Dihydropyrano[2,3-c]imidazo[1,2-a]pyridines with excellent physicochemical and pharmacological properties were identified that represent interesting candidates for further development as potassium-competitive acid blockers (P-CABs). The title compounds were prepared following synthetic pathways that relied either on a Claisen rearrangement/cross-metathesis reaction or on the (asymmetric) reduction of prochiral ketones. The influence of the character of the substituents R3, R6, and Ar on the biological activity and the physicochemical properties of the target compounds was examined. In contrast to the parent system (R6 = H), compounds in which R6 represents a carboxamide residue generally show improved in vivo activity and favorable pKa/log D values. Whereas variation of R3 is useful to obtain target compounds with modified basicity and lipophilicity, strong inhibition of the H+/K+-ATPase and potent in vivo activity is observed for R3 = methyl only. Small modifications of the aryl group, e.g., replacement of hydrogen versus a fluoro atom or a methyl group, are allowed. The (9S)-enantiomers are responsible for the gastric acid secretion inhibiting action, whereas the (9R)-enantiomers are virtually inactive.

Preparation of tetrahydroimidazo[2,1-a]isoquinolines and their use as inhibitors of gastric acid secretion.

A series of novel tetrahydroimidazo[2,1-a]isoquinolines was prepared based on a hetero Diels-Alder reaction between an enamine and 1,2,4-triazine as key step. A structure-activity relationship was established focussing on the influence of the substitution pattern in position 3 and 6 of the heterocycle on antisecretory activity, lipophilicity, and pK(a) value. Potent inhibitors of the gastric acid pump were identified.

[FeIII(tmdta)]--twist-boat/half-chair conformer ratio reliably deduced from DFT-calculated Raman spectra.

The equilibrium between the twist-boat (tb) and half-chair (hc) conformers of the central diamine chelate ring of [Fe(III)(tmdta)]- in solids and aqueous solution has been studied by Raman spectroscopy, supported by calculated Raman spectra using Density Functional Theory.

Novel indanyl-substituted imidazo[1,2-a]pyridines as potent reversible inhibitors of the gastric H+/K+-ATPase.

A series of novel 8-indanylamino- and 8-indanyloxy-substituted imidazo[1,2-a]pyridines with reduced lipophilicity was synthesized from easily accessible starting compounds. The anti-secretory activity of these compounds has been assessed in a competitive binding assay against H(+)/K(+)-ATPase from hog gastric mucosa. Some of the compounds proved to be potent inhibitors of the gastric acid pump.

Mechanistic insights into stereoselective catalysis-the effects of counterions in a CuII-bissulfoximine-catalyzed Diels-Alder reaction.

The initial steps of an enantioselective Diels-Alder reaction catalyzed by a CuII-bissulfoximine complex were followed by EXAFS (EXAFS=extended X-ray absorption fine structure), EPR (EPR=electron paramagnetic resonance) spectroscopy (CW-EPR, FID-detected EPR, pulse ENDOR, HYSCORE; CW=continuous wave; ENDOR=electron nuclear double resonance; HYSCORE=hyperfine sublevel correlation; FID=free induction decay), and UV-visible spectroscopy. The complexes formed between the parent CuX2 (X=Cl-, Br-, TfO-, SbF6-) salts, the chiral bissulfoximine ligand (S,S)-1, and N-(1-oxoprop-2-en-1-yl)oxazolidin-2-one (2) as the substrate in CH2Cl2 were investigated in frozen and fluid solution. In all cases, penta- or hexacoordinated CuII centers were established. The complexes with counterions indicating high stereoselectivity (TfO- and SbF6-) reveal one unique species in which substrate 2 binds to pseudoequatorial positions (via O atoms), shifting the counterions to axial locations. On the other hand, those lacking stereoselectivity (X=Cl- and Br-) form two species in which the parent halogen anions remain at equatorial positions preventing the formation of geometries compatible with those found for X=TfO- and SbF6-.

Spectroscopic investigations of bis(sulfoximine) copper(II) complexes and their relevance in asymmetric catalysis.

The structure of Cu(II) complex 3 formed within the course of a stereoselective Diels-Alder reaction was investigated by EXAFS, CW-EPR at X- and W-band, HYSCORE, pulsed ENDOR, and UV-vis spectroscopy. The experimental techniques indicate that the chiral bis(sulfoximine) ligand (S,S)-1 and the dienophile form a tetragonally distorted complex in CH(2)Cl(2). The ligand binds to the Cu(II) center via the imine nitrogens, whereas the dienophile interacts via the carbonyl oxygen atoms. The additional sites of the first coordination sphere are occupied by counterions and, presumably, solvent molecules. At the axial position, a triflate anion binds via an oxygen atom.

Structural investigation of high-valent manganese-salen complexes by UV/Vis, Raman, XANES, and EXAFS spectroscopy.

XANES and EXAFS spectroscopic studies at the Mn-K- and Br-K-edge of reaction products of (S,S)-(+)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese(III) chloride ([(salen)Mn(III)Cl], 1) and (S,S)-(+)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese(III) bromide ([(salen)Mn(III)Br], 2) with 4-phenylpyridine N-oxide (4-PPNO) and 3-chloroperoxybenzoic acid (MCPBA) are reported. The reaction of the Mn(III) complexes with two equivalents of 4-PPNO leads to a hexacoordinated compound, in which the manganese atom is octahedrally coordinated by four oxygen/nitrogen atoms of the salen ligand at an average distance of approximately 1.90 A and two additional, axially bonded oxygen atoms of the 4-PPNO at 2.25 A. The oxidation state of this complex was determined as approximately +IV by a comparative study of Mn(III) and Mn(V) reference compounds. The green intermediate obtained in reactions of MCPBA and solutions of 1 or 2 in acetonitrile was investigated with XANES, EXAFS, UV/Vis, and Raman spectroscopy, and an increase of the coordination number of the manganese atoms from 4 to 5 and the complete abstraction of the halide was observed. A formal oxidation state of IV was deduced from the relative position of the pre-edge 1s-->3d feature of the X-ray absorption spectrum of the complex. The broad UV/Vis band of this complex in acetonitrile with lambda(max)=648 nm was consistent with a radical cation structure, in which a MCPBA molecule was bound to the Mn(IV) central atom. An oxomanganese(V) or a dimeric manganese(IV) species was not detected.