Using Analytical Technology to Guide Generic Drug Development

the mutant T allele was not associated with an increased risk when treated with budesonide. In contrast, Huang found associations in the GLCCI1 gene among Chinese children with SNPs, rs37969 GG, rs37972 CC, and rs37973 AA producing favourable changes measured by maximal mid-expiratory flow.

Variations among cytochrome p450 (CYP) 3A4, 3A5, and 3A7, which are involved in fluticasone metabolism, were assessed in a study conducted by Stockmann involving a group of Caucasian children. CYP3A5 and CYP3A7 were found to have no association, however, CYP3A4*22 children displayed better asthma control due to the reduced activity of this metabolic enzyme, leading to increased therapeutic outcomes. However, this was not seen in a follow-up study of 64 Caucasian children treated with beclomethasone. Observed in this study were CYP3A5 *1/*1, *1/*3, and *3/*3 variations, with the *3/*3 variant displaying the greatest responsiveness based on asthma control scores. It may be recommended that children with the CYP3A4 *22 initiate therapy with fluticasone. Children with CYP3A5 *3/*3 may be advised to avoid beclomethasoneregimens.

Leukotriene Modifiers (LTM)

Leukotriene modifiers are typically considered when symptoms are uncontrolled by ICS and/or bronchodilators. As seen with previous medications, genetic differences and inter-patient variability also affect a child’s response when given LTM, such as zileuton and montelukast. Although this class may be favoured due to oral administration, nearly half of all children have reported mental status changes like depression and hallucinations. Thus, identifying variants associated with positive LTM response can benefit children who cannot gain symptom control with bronchodilators and ICS.

ALOX5 encodes for 5-lipoxygenase (5-LO) and is found on chromosome 10q11.21. 5-LO is involved in the conversion of arachidonic acid into LTA4 and is the rate limiting step in leukotriene synthesis (Figure 3).Klotsman was able to identify five ALOX5 variants associated with montelukastresponsiveness. However, only two of the five variants were found to be significant for favorable outcomes, SNP rs4987105 TT and rs4986832 AA. Conversely, Telleria recognized five copies of the transcription factor binding sequence GGGCGG (rs59439148)in the ALOX5 promoter region as the major allele. Homozygote wild types (5/5) and heterozygotes (5/4) produced favourable responses to montelukast, while the 4/4 repeats produced unfavourable responses. These children demonstrated higher rates of exacerbation and required more doses of their rescue inhaler (Figure 3).

Organic anion transporter polypeptide 2B1 (OATP2B1) are drug transporters responsible for reuptake of various substrates in the liver, intestine, and kidney. Solute carrier organic anion transporter family member 2B1 (SLCO2B1) encodes for these transporters. Mougey found that those with the SNP, rs12422149 GG genotype demonstrated greater improvement at three and six months compared to the those with the AG genotype. Similarly, a study by Li with 50 asthmatic Chinese children displayed lower montelukast clearance if possessing the SLCO2B1 rs12422149 GG genotype, compared to either GA and AA. Due to increased plasma concentrations, children with the GG genotype found better symptom relief when given montelukast. Although CYP2C8 variations were also investigated in this study, no associations with montelukast response were found.

2, Barnes, P.J. Inhaled Corticosteroids. Pharmaceuticals2010, 3, 514–540 3, Mougey, E.; Lang, J.E.; Allayee, H.; Teague, W.G.; Dozor, A.J.; Wise, R.A.; Lima, J.J. ALOX5 polymorphism associates with increased leukotriene production and reduced lung function and asthma control in children with poorly controlled asthma.Clin. Exp. Allergy 2013, 43, 512–520

Figure3: Leukotriene Modifiers Mechanism of Action. Adapted from3 .

Outlook

The cost effectiveness and increased quality of life due to pharmacogenomic testing in adults has been clearly demonstrated for those who are genetically inclined to show a reduced response to ICS. Although no research has been conducted in the paediatric population for the same outcomes, identifying children who may also be predisposed to ICS unresponsiveness can encourage providers to initiate LTM therapy sooner. This would eliminate the trial and error of increasing doses of a medication class that the patient will likely fail. Additionally, drug transporters and CYP450 enzymes have potential to guide clinicians when selecting medications.

Unfortunately, limitations in many of these studies include the small sample size, unstandardised outcome measures, and lack of diversity. With recent discussions on race and ethnicity, there is a need for further stratification based on genetic ancestry. Larger paediatric asthmatic studies could improve confidence for the translation of genotype to phenotype, with the common goal of developing the best course of treatment for each individual child. Although preemptive pharmacogenomic testing for asthma is not currently recommended, the hope for universal testing at an early age has the potential to eliminate prolonged medication trial and error.

AUTHOR BIO

Christy Lim is a PY4 pharmacy student at the Massachusetts College of Pharmacy and Health Sciences University-Boston. Her research interests include pharmacogenomics in both adult and paediatric populations. References available at www.pharmafocusasia.com

Ronny Priefer is a Full Professor of Medicinal Chemistry and Dean of Graduate Studies at the Massachusetts College of Pharmacy and Health Sciences University-Boston with over 90 peer-reviewed publications. Additionally he is a serial entrepreneur, with five start-up companies and over half a dozen patents.

Product deformulation is a crucial but challenging process for the development of generic products. This article will discuss how deformulation uses analytical technologies to decode the physicochemical formation of a drug and provide insight into how its composition might affect drug efficacy and safety in vivo.

Paul Kippax, Pharmaceutical and Food Sector Director, Malvern Panalytical

As is the case in most scientific disciplines, the most common way to determine how something works is to break it down, identify and quantify its component parts and then see how they work together to function as a whole. This is true for understanding the metabolism of a cell, for understanding the synthesis of a chemical, and in the pharmaceutical industry, for understanding the formulation and function of reference listed drugs (RLDs).

The reverse engineering of an RLD— product deformulation—is a critical step in the development of more accessible and less expensive generic versions. Deformulation relies on analytical technologies to not only tease apart the physicochemical properties of an innovator drug and its constituent parts—its active pharmaceutical ingredients (APIs) and excipients—but also offer drug developers insights into how the innovator RLD was manufactured. Such information is vital to drug companies competing to develop generic alternatives as drug products approach or pass patent expiration.

In this article, we will examine the use of analytical technologies in generic drug development focusing on the example of Morphologically-Directed Raman Spectroscopy (MDRS), to show how these techniques can help drug developers decode both the formulation and manufacturing processes of RLDs.

Unveiling the blueprint

Guiding the workflows associated with generic drug development, the FDA’s Critical Path Opportunities for Generic Drugs emphasises the need for companies to adopt a Quality-by-Design (QbD) approach (1), which demands a thorough understanding and control of the variables impacting product and process behaviours. To accomplish this, developers must gather extensive information about the innovator drug, and generate data using a variety of in vitro analytical methods.

These methods help developers create a comprehensive blueprint that captures the complexity of a drug product’s constituents and how these interact, creating a microstructure which ensures the stability and effective delivery of the drug. With these critical material attributes at hand, developers can begin to design a generic product and, in some cases, may even consider reformulating the product in the hope of improving its clinical efficacy and/or safety profile.

The constituents of any drug product fall into one of two categories: excipients and APIs. Excipients can sometimes be added to a drug formulation to act simply as a bulking agent to help with achieving a consistent concentration of API in each dose. However, excipients can also be functional agents, improving the stability of the drug and altering its delivery to the patient. Examples of this include controlled-release agents, stabilisers and surface-active agents, which can alter how and how quickly an API reaches and is absorbed by its target tissues.

Developers use technologies such as laser diffraction and analytical imaging to both characterise and differentiate the excipients from other RLD components and one another, information vital to generic development and possible reformulation. When exploring reformulation, developers rely on these analytical technologies to ensure that efforts to improve one feature of a drug were not deleterious to other features.