Drug Substance Manufacturing Research Articles

What happened: The chemistry side of the incident with EMS contamination in Viracept tablets

A technical review of the events leading to the global recall of Viracept film coated tablets 250 mg in June 2007 is given from the drug substance manufacturing perspective. Root cause analysis performed and corrective actions implemented are presented. Using the decay rate of ethyl methane sulfonate in Viracept film coated tablets 250 mg at 25 °C derived from stability studies, establishing of the worst case scenario for patient exposure to ethyl methane sulfonate, is outlined. Whereas the first evaluation based on ethyl methane sulfonate levels found in the drug substance suggested a worst case patient exposure of 2300 ppm, the decay rate of ethyl methane sulfonate in the drug product and the time gap between drug product manufacture and earliest possible use by patients led to the conclusion that 920 ppm (±10%) over a period of approx. 90 days is a reasonably cautious assumption for the worst case patient exposure scenario.

Debottlenecking the Synthesis Route of Asenapine

The discovery synthesis of asenapine that was used for the manufacture of drug substance batches up to 10 kg contained two chemical steps that were major bottlenecks for scale-up. One of these steps involved a magnesium/methanol reduction of an enamide moiety that was severely hampered by safety and efficiency problems. The other step was a laborious chromatography and isomerization cycle that was marked by a poor yield and extremely low throughput. The safety issues of the magnesium/methanol reduction could be solved by adding portions of magnesium to a solution of the enamide. In addition, an alternative process for the conversion of the mixture of cis- and trans-lactam into the desired trans-isomer was developed, circumventing the chromatographic separation.

Quantification of some active compounds in air samples at pharmaceutical workplaces by HPLC

Workers involved in the manufacture of drug substances may be exposed to active pharmaceuticals by inhalation of drug dusts or droplets which has been considered the main exposure route. The proposed HPLC method allowed to determine sulpiryde, hydroxyurea and dyprophylline in the concentration range of 0.01–0.187 mg/m 3, 0.001–0.08 mg/m 3 and 0.01–0.40 mg/m 3 for sulpiryde, hydroxyurea and dyprophylline, respectively, when 480 L of air sample was collected on the glass fibre filters. Sulpiryde was extracted with a solvent system consisting of acetonitrile–phosphate buffer at pH 3 (85:15, v/v), while the best efficiency of extraction for hydroxyurea and dyprophylline was achieved using water. HPLC analysis of sulpiryde with fluorescence detection was more sensitive (LOD = 3.1 μg/L) in comparison with UV detection (LOD = 84.4 μg/L).

Identification of Fmoc‐β‐Ala‐OH and Fmoc‐β‐Ala‐amino acid‐OH as new impurities in Fmoc‐protected amino acid derivatives*

During the manufacture of a proprietary peptide drug substance a new impurity appeared unexpectedly. Investigation of its chemical structure established the impurity as a beta-Ala insertion mutant of the mother peptide. The source of the beta-Ala was identified as contamination of the Fmoc-Ala-OH raw material with Fmoc-beta-Ala-Ala-OH. Further studies also demonstrated the presence of beta-Ala in other Fmoc-amino acids, particularly in Fmoc-Arg(Pbf)-OH. In this case, it was due to the presence of both Fmoc-beta-Ala-OH and Fmoc-beta-Ala-Arg(Pbf)-OH. It is concluded that beta-Ala contamination of Fmoc-amino acid derivatives is a general and hitherto unrecognized problem to suppliers of Fmoc-amino acid derivatives. The beta-Ala is often present as Fmoc-beta-Ala-OH and/or as a dipeptide, Fmoc-beta-Ala-amino acid-OH. In collaboration with the suppliers, new specifications were introduced, recognizing the presence of beta-Ala-related impurities in the raw materials and limiting them to acceptable levels. The implementation of these measures has essentially eliminated beta-Ala contamination as a problem in the manufacture of the drug substance.

The intramolecular asymmetric Pauson-Khand cyclization as a novel and general stereoselective route to benzindene prostacyclins: synthesis of UT-15 (treprostinil).

A general and novel solution to the synthesis of biologically important stable analogues of prostacyclin PGI(2), namely benzindene prostacyclins, has been achieved via the stereoselective intramolecular Pauson-Khand cyclization (PKC). This work illustrates for the first time the synthetic utility and reliability of the asymmetric PKC route for synthesis and subsequent manufacture of a complex drug substance on a multikilogram scale. The synthetic route surmounts issues of individual step stereoselectivity and scalability. The key step in the synthesis involves efficient stereoselection effected in the PKC of a benzoenyne under the agency of the benzylic OTBDMS group, which serves as a temporary stereodirecting group that is conveniently removed via benzylic hydrogenolysis concomitantly with the catalytic hydrogenation of the enone PKC product. Thus the benzylic chiral center dictates the subsequent stereochemistry of the stereogenic centers at three carbon atoms (C(3a), C(9a), and C(1)).

Automation of Solid form Screening Procedures in the Pharmaceutical Industry—How to Avoid the Bottlenecks

Solid form selection is one of the key milestones in the development of any new small molecule drug candidate. It is critical not only from a regulatory perspective but also from a drug substance manufacturing and drug product-processing viewpoint. High throughput systems provide a significant increase in the number and diversity of experiments performed on a given compound, and are becoming a central feature of drug development, especially in areas concerned with solid form selection. This paper reports our automation of the polymorph screening procedure in combination with automated isolation of samples. Particular focus is placed on the analysis by high throughput PXRD with associated strategies for analysis, clustering, pattern classification, and visualization

Application of the Multivariate T2 Control Chart and the Mason–Tracy–Young Decomposition Procedure to the Study of the Consistency of Impurity Profiles of Drug Substances

A case study from the chemical and pharmaceutical industry is used to show the value of the application of the multivariate T 2 control chart and the Mason–Tracy–Young decomposition procedure to the study of the consistency of the impurity profiles of drug substances. The impurity profile of a drug substance is one of the most important quality characteristics, is almost always multivariate in nature, and is complicated by the relationships among the impurity levels. This prohibits examining each impurity by univariate statistical procedures. Several of the possible benefits of applying these multivariate statistical procedures to the manufacture of drug substances are illustrated through the presentation and discussion of the case study.

NMR characterization of a novel bile acid sequestrant, DMP 504.

DMP 504, a potential bile acid sequestrant for the treatment of hypercholesterolemia, is a highly insoluble, cross-linked polymer which does not lend itself to ordinary means of characterization used for drug substances in the pharmaceutical industry. Therefore, alternative characterization techniques have been sought. As part of an effort into extensive characterization of DMP 504 drug substance, nuclear magnetic resonance (NMR) was employed to provide insight into details of the DMP 504 polymer structure. The primary motivation for determining the structure of the polymer chain is to relate the DMP 504 structure to its performance properties as a bile acid sequestrant. Characterization of the polymer chain and understanding of the structural basis of its properties is essential in optimizing and controlling the manufacture of reproducible drug substance. NMR has proven a versatile tool for the description of polymer structure and dynamics because of the wide range of nuclear interactions affecting the NMR signal. This allows the design of experiments to elicit information about specific polymer interactions or properties. The methods of sample preparation utilized to obtain NMR spectra of the insoluble polymer, as well as a discussion and comparison of results for the characterization of DMP 504 obtained using several different NMR techniques will be presented.

Production of (R)-Aminoglutethimide: A New Route from 1-Chloro-4-nitrobenzene

The development of a short, safe and enantioselective route for the preparation of (R)-aminoglutethimide is described. The process was designed for economic large-scale manufacture of the bulk drug substance to acceptable quality standards, to allow clinical evaluation of the single enantiomer over the existing racemate. (R)-Aminoglutethimide was prepared from 1-chloro-4-nitrobenzene using a six-stage synthetic sequence, via chemoresolution of key intermediate racemic 4-cyano-4-(4-nitrophenyl)hexanoic acid using (−)-cinchonidine. The process allowed for preparation of several kilograms of the precursor (R)-nitroglutethimide, to cGMP at pilot-plant scale, along with demonstration of the final hydrogenation step to (R)-aminoglutethimide in the laboratory. This route avoids the problems of hazardous nitration technology, and therefore regio-isomer contamination of the product, associated with other procedures. The resolution chemistry described represents an improvement on literature procedures. Optimisation...

Significance of controlling crystallization mechanisms and kinetics in pharmaceutical systems

Metastable thermodynamic states are frequently encountered in pharmaceutical systems, in the intentional or unintentional creation of supersaturation, in the crystallization of desired solid-state modifications, and in the control of solid-phase conversions during isolation, manufacturing, storage, and dissolution.1-4 Some examples in which metastable states are encountered include solid solutions, freeze-concentrated solutions, solutions of weak acids or bases exposed to a pH change, solutions prepared by dissolving a solid-state modification with a higher solubility (higher free energy), and residual solutions during filtration, granulation, and drying. Because crystallization provides a way of reducing the free energy of metastable thermodynamic states, the extent to which metastable states can be maintained is determined by the crystallization mechanisms and kinetics.5-16 What is surprising, however, is that despite the important role that crystallization has in process control and in determining solid-phase outcomes, crystallization phenomena are often neglected in the pharmaceutical industry until a problem is encountered. While emphasis is often given to the knowledge of equilibrium phase diagrams with the purpose of identifying the concentration and temperature regions of thermodynamic stability of solid phases, information on crystallization processes can only be obtained by combining studies of thermodynamic properties with kinetic measurements. Cases of unwanted or previously unknown nucleation events abound. Dunitz and Bernstein17 documented cases of “disappearing or elusive polymorphs” that provide evidence for the consequences of poor process control in crystallization of polymorphic systems. The recent shortage in the supply of capsules of the HIV protease inhibitor Norvir (indinavir), due to the sudden formation of a crystalline structure different from the one harvested for months,18 illustrates the decisive role that nucleation mechanisms and kinetics have on crystallization. Nichols and Frampton19 have reported considerable efforts that failed to crystallize the metastable polymorph of paracetamol as described in the initial publication of the crystal structure.20 The critical role of crystallization kinetics in determining the appearance of crystalline modifications is also recognized by the FDA and described in the guidelines for the manufacture of drug substances:21 “Appropriate manufacturing and control procedures (including in-process testing when needed) should be established for the production of the desired solid-state form(s). It should be emphasized that the manufacturing process (or storage condition) is responsible for producing particular polymorphs or solvates; the control methods merely determine the outcome.” Even when the parameters that regulate crystallization phenomena are neglected, the illusion of process control is motivated by a crystallization process that yields the desired productssolid phase modification, shape, or size distributionsand by the robust analytical methods used for solid state characterization. This situation is greatly complicated by the recent emphasis on an exclusively * Corresponding author. Tel: 734-763-0101. Fax: 734-763-2022. e-mail: nrh@umich.edu. † University of Michigan. ‡ Dupont Pharmaceuticals. July 1999

Validation in Research and Development —What is Appropriate?

Validation is a concept that has expanded considerably in scope since the mid-1970s (1–5). It has a nebulous quality caused by differing definitions, interpretations of guidelines, nomenclature and perceived changes in application. Initially introduced to assure the processes used in commercial drug product manufacture, validation requirements inexorably began to include the equipment, facilities and utilities supporting those processes. Subsequently, the need for validation has spread to both earlier in the production chain (drug substance manufacture) and to earlier in the development process (research, development and pilot operations and supporting analytical laboratories). It is now established that validation is required for the manufacture of drug substances and drug products according to Good Manufacturing Practices (GMPs), for use in clinical trials and also to assure the data from preclinical studies conducted to Good Laboratory Practices (GLPs). The problem is to translate the rules devised for routine production and apply them to research and development (R&D). This paper describes the hierarchical structure of validation as applied to GMP operations, details how programmes are administered and executed and suggests how much validation is expected by the regulatory authorities for both GMP and GLP activities. Also included are brief accounts of computer and cleaning validation as applied to research and development.

Development and validation of analytical methodology for near-infrared conformance testing of pharmaceutical intermediates

An approach was developed to create and validate analytical methods to perform near-infrared (NIR) conformance testing on two isolated intermediates used in the manufacture of loracarbef monohydrate bulk drug substance. Method calibration sets were developed from second-derivative NIR reflectance spectra for 30 representative batches of each intermediate. In conformance testing, second-derivative NIR spectra for samples from newly manufactured batches are compared with the calibration set. If the new spectrum is not statistically different to the average of the calibration set, the sample passes the conformance test. Using authentic batch samples of typical and low-potency lots, the methods were validated for accuracy, selectivity, ruggedness and repeatability of the methods.

Drug substance manufacture process control: application of flow injection analysis and HPLC for monitoring an enantiospecific synthesis

Effective process control can only be achieved through an understanding of the operating issues of the reaction. The development and use of effective and rugged analytical methods is necessary to monitor these parameters. The intent of this paper is to present some key analytical issues encountered in the synthesis of MK-0679, an LTD 4 antagonist. In a key step of the compound's synthesis, a prochiral diester intermediate undergoes an enantioselective enzymatic hydrolysis (in the presence of Triton X-100) leading to the ( S)-ester acid. Subsequent processing transforms the ester acid into the final product. The residual amount of the detergent in the final product, the rapid determination of the enzymatic activity and the optical purity of the final product emerged as key issues in the control of the reaction. As a solution, two techniques were utilized and are presented: flow injection analysis and HPLC.

Cancer Gene Therapy Using Plasmid DNA: Purification of DNA for Human Clinical Trials

A production method has been developed for the purification of pharmaceutical-grade plasmid DNA for in vivo gene therapy. This method has been applied to the purification of VCL-1005, which is a eukaryotic plasmid expression vector that codes for the production of the HLA-B7 protein. Purified VCL-1005 is formulated with a cationic lipid and injected directly into established tumors of HLA-B7-negative patients with advanced cancers to heighten the patient's immune response against the cancer. The purification of pharmaceutical-grade plasmid DNA requires the development of highly reproducible and scaleable processing methods that meet regulatory standards similar to those required for the manufacture of recombinant protein pharmaceuticals. Defined pharmaceutical standards of purity, potency, efficacy, and safety are routinely met by the process described in this study. The scaleable purification method described here is a combination of highly reproducible unit operations; alkaline lysis, precipitation, and size-exclusion chromatography. The advantages over existing DNA purification methods include improved plasmid purity and the elimination of undesirable process additives such as toxic organic extractants and animal-derived enzymes. The overall process yield of purified plasmid DNA from fermentation through final column purified product is greater than 50%. Contaminating Escherichia coli DNA levels are reproducibly below 1% as measured by Southern analysis. Endotoxin levels are less than 0.03 endotoxin units/micrograms plasmid DNA and residual protein is undetectable. This process was used to produce 100 mg of VCL-1005 for use in an active clinical protocol.

Effects of FDA Inspections on Chemical Development

The FDA regulations, even though written with the drug product in mind, are applied more and more to the manufacture of drug substances. The FDA would like to see written evidence that the synthetic process is well understood and under control, since a well-developed process assures reproducible quality of the drug substance. It is the responsibility of chemical development to write such a development report which includes process validation. This paper describes a development report with illustrative examples and defines the concept of drug substance process validation. The effects the new FDA guidelines will have on chemical development are a lot more documentation and a little more experimentation in the area of process validation.