Conformational isomerism in solid state of AMG 853--structure studies using solid-state nuclear magnetic resonance and X-ray diffraction.

Investigation of an additional resonance peak in the (19) F solid-state nuclear magnetic resonance (NMR) spectrum of AMG 853, a dual antagonist of DP and CRTH2 previously in clinical development for asthma, has led to the identification of two conformational isomers coexisting in the crystal lattice in a continuous composition range between 89.7%:10.3% and 96.5%:3.5%. These two isomers differ in the chloro-flurorophenyl moiety orientation-the aromatic ring is flipped by 180° in these two isomers. The level of the minor isomer is directly measured through integration of the two peaks in the (19) F solid-state NMR spectrum. The values obtained from the NMR data are in excellent agreement with the degree of disorder of the fluorine atom in the crystal structure, refined using both single-crystal and high-resolution powder X-ray diffraction data.

High-throughput 96-well solvent mediated sonic blending synthesis and on-plate solid/solution stability characterization of pharmaceutical cocrystals.

A 96-well high-throughput cocrystal screening workflow has been developed consisting of solvent-mediated sonic blending synthesis and on-plate solid/solution stability characterization by XRPD. A strategy of cocrystallization screening in selected blend solvents including water mixtures is proposed to not only manipulate solubility of the cocrystal components but also differentiate physical stability of the cocrystal products. Caffeine-oxalic acid and theophylline-oxalic acid cocrystals were prepared and evaluated in relation to saturation levels of the cocrystal components and stability of the cocrystal products in anhydrous and hydrous solvents. AMG 517 was screened with a number of coformers, and solid/solution stability of the resulting cocrystals on the 96-well plate was investigated. A stability trend was observed and confirmed that cocrystals comprised of lower aqueous solubility coformers tended to be more stable in water. Furthermore, cocrystals which could be isolated under hydrous solvent blending condition exhibited superior physical stability to those which could only be obtained under anhydrous condition. This integrated HTS workflow provides an efficient route in an API-sparing approach to screen and identify cocrystal candidates with proper solubility and solid/solution stability properties.

Crystal structure study and investigation of solid-state cyclization for AMG 222, a channel hydrate.

In this study, we investigate the solid-state structure and stability of AMG 222 (5-(2-[2-(2-cyano-pyrrolidin-1-yl)-2-oxo-ethylamino]-propyl)-5-(1H-tetrazol-5-yl)-10,11-dihydro-5H-dibenzo[a,d]cycloheptene-2,8 dicarboxylic acid bisdimethylamide), a small molecule DPP-IV inhibitor. Crystal structure of AMG 222 has been solved from single crystal X-ray analysis. Crystallographic data are as follows: monoclinic, P2(1) (no. 4), a=9.0327(5)Å, b=18.6177(8)Å, c=21.4927(10)Å, ß=90.126(3)°, V=3614.4(3)Å(3), Z=4. Based on single crystal structure, AMG 222 is a pentahydrate with the water molecules sitting in channels formed by the drug framework. There are three distinct crystal structures of AMG 222 between 0 and 95% relative humidity (RH), namely the anhydrate, hemihydrate, and pentahydrate forms. Solid-state stability of the GMP batch showed a high level of cyclized degradation product. It was postulated that the degradation was promoted by increased amorphous content generated as a result of excessive drying that was employed to remove residual crystallization solvent. Material produced using a modified procedure using a humidified nitrogen purge had lower amorphous content and lower levels of cyclic degradation when compared to the GMP batch.

Discovery of dehydro-oxopiperazine acetamides as novel bradykinin B1 receptor antagonists with enhanced in vitro potency.

In a series of bradykinin B1 antagonists, we discovered that replacement of oxopiperazine acetamides with dehydro-oxopiperazine acetamides provided compounds with enhanced activity against the B1 receptor. The synthesis and SAR leading to potent analogs with reduced molecular weight will be discussed.

Manufacture and performance evaluation of a stable amorphous complex of an acidic drug molecule and Neusilin.

In this paper, we explore the use of Neusilin, an inorganic magnesium aluminometasilicate, to stabilize the amorphous form of an acidic drug Sulindac. Both cryomilling and ball milling of the drug with Neusilin were found to produce the amorphous phase. However, the ball-milled (BM) material exhibited superior physical stability when compared with the cryomilled material at 40°C/75% relative humidity. (13) C solid-state nuclear magnetic resonance investigation of the BM material revealed an acid-base reaction between Sulindac and Neusilin. Optimal milling conditions and the kinetics of salt formation were also established. As benchtop milling is a laboratory-scale process, a scalable process was developed to make Sulindac-Neusilin amorphous drug complex using hot-melt extrusion (HME). The dissolution properties of the resulting HME material was found to have been improved over the material made by benchtop milling while maintaining similar physical stability. The HME material was used to make tablets using a direct compression method. The HME tablets were found to have better dissolution properties than tablets made from crystalline Sulindac. For the broad class of acidic drugs containing the carboxyl moiety, inorganic silicates such as Neusilin would offer a better choice than organic polymers to stabilize the amorphous phase.

3-Oxo-2-piperazinyl acetamides as potent bradykinin B1 receptor antagonists for the treatment of pain and inflammation.

The discovery of novel and highly potent oxopiperazine based B1 receptor antagonists is described. Compared to the previously described arylsulfonylated (R)-3-amino-3-phenylpropionic acid series, the current compounds showed improved in vitro potency and metabolic stability. Compound 17, 2-((2R)-1-((4-methylphenyl)sulfonyl)-3-oxo-2-piperazinyl)-N-((1R)-6-(1-piperidinylmethyl)-1,2,3,4-tetrahydro-1-naphthalenyl)acetamide, showed EC(50) of 10.3 nM in a rabbit biochemical challenge model. The practical syntheses of chiral arylsulfonylated oxopiperazine acetic acids are also described.

Discovery of 2,4-bis-arylamino-1,3-pyrimidines as insulin-like growth factor-1 receptor (IGF-1R) inhibitors.

The insulin-like growth factor-1 receptor (IGF-1R) plays an important role in the regulation of cell growth and differentiation, and in protection from apoptosis. IGF-1R has been shown to be an appealing target for the treatment of human cancer. Herein, we report the synthesis, structure-activity relationships (SAR), X-ray cocrystal structure and in vivo tumor study results for a series of 2,4-bis-arylamino-1,3-pyrimidines.

Discovery of a potent, orally active 11beta-hydroxysteroid dehydrogenase type 1 inhibitor for clinical study: identification of (S)-2-((1S,2S,4R)-bicyclo[2.2.1]heptan-2-ylamino)-5-isopropyl-5-methylthiazol-4(5H)-one (AMG 221).

Thiazolones with an exo-norbornylamine at the 2-position and an isopropyl group on the 5-position are potent 11beta-HSD1 inhibitors. However, the C-5 center was prone to epimerization in vitro and in vivo, forming a less potent diastereomer. A methyl group was added to the C-5 position to eliminate epimerization, leading to the discovery of (S)-2-((1S,2S,4R)-bicyclo[2.2.1]heptan-2-ylamino)-5-isopropyl-5-methylthiazol-4(5H)-one (AMG 221). This compound decreased fed blood glucose and insulin levels and reduced body weight in diet-induced obesity mice.

Fast surface crystallization of amorphous griseofulvin below T g.

PURPOSE: To study crystal growth rates of amorphous griseofulvin (GSF) below its glass transition temperature (T (g)) and the effect of surface crystallization on the overall crystallization kinetics of amorphous GSF. METHODS: Amorphous GSF was generated by melt quenching. Surface and bulk crystal growth rates were determined using polarized light microscope. X-ray powder diffraction (XRPD) and Raman microscopy were used to identify the polymorph of the crystals. Crystallization kinetics of amorphous GSF powder stored at 40 degrees C (T (g)-48 degrees C) and room temperature (T (g)-66 degrees C) was monitored using XRPD. RESULTS: Crystal growth at the surface of amorphous GSF is 10- to 100-fold faster than that in the bulk. The surface crystal growth can be suppressed by an ultrathin gold coating. Below T (g), the crystallization of amorphous GSF powder was biphasic with a rapid initial crystallization stage dominated by the surface crystallization and a slow or suspended late stage controlled by the bulk crystallization. CONCLUSIONS: GSF exhibits the fastest surface crystallization kinetics among the known amorphous pharmaceutical solids. Well below T (g), surface crystallization dominated the overall crystallization kinetics of amorphous GSF powder. Thus, surface crystallization should be distinguished from bulk crystallization in studying, modeling and controlling the crystallization of amorphous solids.

Multiple approaches to pharmaceutical polymorphism investigation--a case study.

Polymorph screening of Compound A, an investigational drug, revealed two anhydrous polymorphs (Forms I and II) and two monohydrates (Forms III and IV) of this pharmaceutical solid. The physiochemical properties of the four forms were characterized by thermal analysis, hot-stage microscopy, equilibrium solubility and intrinsic dissolution rate measurements, and X-ray powder diffraction. Inter-conversion relationship of the four forms was fully elucidated. Thermodynamic stability relationship was inferred from melting data for Form I and Form II and evaluated by van't Hoff plot for Form III and Form IV. Form I and Form III were found to be the more stable anhydrous and hydrate form, respectively. Anhydrous Form I was selected for further pharmaceutical development.

A quantitative kinetic study of polysorbate autoxidation: the role of unsaturated fatty acid ester substituents.

PURPOSE: To study the role of unsaturated fatty acid ester substituents in the autoxidation of polysorbate 80 using quantitative kinetics. METHODS: Oxidation kinetics were monitored at 40 degrees C in aqueous solution by tracking head space oxygen consumption using a fiber optic oxygen sensor with phase shift fluorescence detection. Radical chain initiation was controlled using an azo-initiator and assessed by Hammond's inhibitor approach, allowing oxidizability constants (k(p)/(2k(t))(1/2)) to be isolated. Reaction orders were determined using modified van't Hoff plots and mixed polysorbate micelles. RESULTS: The oxidizability constant of polysorbate 80 ((1.07 +/- 0.19) x 10(-2) M(-1/2) s(-1/2)) was found to be 2.65 times greater than polysorbate 20 ((0.404 +/- 0.080) x 10(-2) M(-1/2) s(-1/2)). The additional reactivity of polysorbate 80 was isolated and was first-order in the unsaturated fatty acid ester substituents, indicating that the bulk of the autoxidative chain propagation is due to these groups. This data, and the observation of a half-order dependence on the azo-initiator, is consistent with the classical autoxidation rate law (-d[O(2)]/dt = k(p)[RH](R(i)/2k (t))(1/2)). CONCLUSIONS: Polysorbate 80 autoxidation follows the classical rate law and is largely dependent on the unsaturated fatty acid ester substituents. Clarification of the substituents' roles will aid formulators in the selection of appropriate polysorbates to minimize oxidative liabilities.

Quantification of compaction-induced crystallinity reduction of a pharmaceutical solid using 19F solid-state NMR and powder X-ray diffraction.

(19)F solid-state nuclear magnetic resonance (NMR) was investigated as an analytical technique to quantify the amorphous phase in a fluorine-containing pharmaceutical candidate. The crystallinity of Compound 1 was calculated using two (19)F T(1) relaxation-based methods. The first method employs both the pure amorphous and the crystalline reference standards while the second method is model independent and utilizes a single standard. The (19)F solid-state NMR results were confirmed with powder X-ray diffraction methods. From X-ray diffraction data, two linear calibration curves were obtained from blends of crystalline and amorphous Compound 1: one is based on the total integrated intensity of selected diffraction peaks and the other on the total intensity of the amorphous halo at 2theta positions that have no interference from crystalline diffraction peaks. The crystallinity of Compound 1 after compaction calculated by both (19)F solid-state NMR methods was in excellent agreement with the results from the X-ray calibration curves. (19)F solid-state NMR was shown to be a powerful technique in determining the amount of amorphous phase present in a pharmaceutical solid.

Crystal structure, crystal morphology, and surface properties of an investigational drug.

In this study we investigated the correlations between the single crystal structure, the crystal habit and morphology, and surface energetics of an investigational pharmaceutical compound. Crystal structures of both the anhydrous form (Form A) and monohydrate form (Form B) have been solved from single crystal X-ray analysis. The external morphology of Form A solid was predicted by molecular modeling using attachment energies to be thick plate-like with two dominant faces (100) and (002). The external morphology of Form B was predicted to be needle-like with a dominant face (101 ). The predicted morphologies were confirmed by optical micrographs and the Miller indices of the dominant faces were complemented by X-ray powder diffraction (XRPD) method. Contact angle measurements showed that the anhydrous form has better wettability as predicted from crystal structure and morphology.

Quantitative determination of solid-state forms of a pharmaceutical development compound in drug substance and tablets.

Common analytical techniques including Raman, NIR, and XRD were evaluated for quantitative determination of three solid-state forms (amorphous, Form B and Form C) of a development compound. Raman spectroscopy was selected as the primary analytical technique with sufficient sensitivity to monitor and quantify the neat drug substance alone and in the drug product. A reliable multivariate curve resolution (MCR) method based on the second derivative Raman measurements of the three pure physical forms was developed and validated with 3.5% root mean square error of prediction (RMSEP) for Form B, which was selected as the preferred form for further development. A partial least squares (PLS) algorithm was also used for the multivariate calibration of both the NIR and Raman measurements. The long-term stability of Form B as a neat active pharmaceutical ingredient (API) and in a tablet formulation was quantitatively monitored under various stress conditions of temperature and moisture. Moisture, temperature, excipients and compression were found to have significant effects on the phase transition behavior of Form B.

Preparation of 1-(3-aminobenzo[d]isoxazol-5-yl)-1H-pyrazolo[4,3-d]pyrimidin-7(6H)-ones as potent, selective, and efficacious inhibitors of coagulation factor Xa.

Previously, potent factor Xa inhibitors were described based on the 1H-pyrazolo[4,3-d]pyrimidin-7(6H)-one bicyclic core and a 4-methoxyphenyl P1 moiety. This manuscript describes 1H-pyrazolo[4,3-d]pyrimidin-7(6H)-one and related bicyclic cores with the 3-aminobenzisoxazole P1 moiety. Many of these compounds are potent, selective, and efficacious inhibitors of coagulation factor Xa.

High-throughput logP measurement using parallel liquid chromatography/ultraviolet/mass spectrometry and sample-pooling.

A novel approach to high-throughput logP measurement based on liquid chromatography/ultraviolet/mass spectrometry (LC/UV/MS) is proposed. The logP value is determined by correlation with the logk value, where k is the capacity factor k = (t(r)-t(0))/t(0), with the logP value using a defined set of standards. Since the analyte retention time (t(r)) is determined from the appropriate extracted ion chromatogram (EIC), there are no interferences from impurities and this allows the pooling of multiple compounds into one injection. To ensure the accuracy and instrument robustness in a routine high-throughput environment, a simple and MS-friendly mobile phase consisting of 20 mM ammonium carbonate (pH 8.0) for basic compounds or 20 mM ammonium formate (pH 1.0) for acidic compounds, both in combination with methanol at a ratio of 45:55, is used. This approach has been successfully used on single as well as parallel multi-channel LC/UV/MS systems to screen small to large sets of lead compounds and their analogs. A high-throughput capability to analyze over 1000 compounds per day has been achieved.