Case Studies and Client Projects
Latest Case Studies
We’ve observed an increase in requests for synthesis of N-glucuronides over the last couple of years. We speculate that this may be due to the increasing use of N-heterocyclic chemistry in the design of new small molecule drugs, and pan company strategies to reduce CYP metabolism. The situation is further complicated by the high interspecies variability in formation of some N-glucuronides, especially aliphatic tertiary amines and aromatic N-heterocycles. UGT1A4 and UGT2B10 are key enzymes responsible for N-glucuronidation reactions in humans, rates of which can be much higher than in other animals. To compound this, synthesis of N-glucuronides is not always straightforward, and can be further muddied by metabolite stability issues, complicating interpretation of data.
Lorcaserin is a selective 5-HT2C receptor agonist acting on the hypothalamus to reduce appetite and treat obesity, but which has now been withdrawn from the market. Lorcaserin N-sulfamate (M1) is the major circulating metabolite in plasma with lorcaserin N-carbamoyl glucuronide (M5) being the major excretory metabolite in urine. Screening of lorcaserin against Hypha’s panels of microbes and liver S9 preps gave scalable routes to accessing both metabolites.
There has been a notable increase in metabolism of new drug candidates through non-CYP phase I pathways such as those mediated via aldehyde oxidase (AO).1 Further, mixed AO/P450 substrates may be subject to metabolic shunting, an important consideration during toxicology and DDI assessment of these drugs.2 Access to metabolites may thus be important to consider for drugs with mixed metabolism.
It is well known that metabolites of drug compounds may have different efficacy and properties to that of the parent compound. Investigation and production of these metabolites is critical for exploration and understanding of SAR, and to ensure thorough patent coverage. Metabolites can also be sourced to create antibodies used in development of assays for therapeutic drug monitoring.
Access to multiple metabolites needed to support clinical development is not always straightforward, and can sometimes mean that more than one technique needs to be applied to fulfil requirements. In one such project, a US pharma client required > 200 mg of three metabolites of a drug; an N-glucuronide (M1), an indirect O-glucuronide (M2b) and a hydroxylated metabolite (M8b). As part of this project, multiple components of Hypha’s one-stop metabolite shop were employed, including chemical synthesis, microbial biotransformation as well as purification and structure elucidation by NMR.
If clearance mechanisms of the test drug results in sufficient quantities of the major metabolites in biological material such as faeces or urine, purification and subsequent identification of metabolites from such matrices is possible. One such project undertaken at Hypha resulted in tens of milligrams of the R- and S-O-glucuronides of carisbamate, a neuromodulator developed by SK Life Science, which were purified to >95% purity from 150 ml of urine using a three-step purification method.
Metabolites of some agrochemical products such as pesticides and herbicides possess greater plant or mammalian toxicity compared to the parent compound, thus necessitating a need for their identification, study and provision of analytical reference standards to meet regulatory requirements. Where a synthetic route is challenging, or the identity of a metabolite is unknown, creation of metabolites by microbial biotransformation is often a successful alternative due to similarities of xenobiotic metabolism in mammals, birds, fish, soil, and to some extent, plants.1 Furthermore, biocatalysis affords aromatic and aliphatic site-selectivity as well as regiocontrol of aromatic hydroxylation.2
The FDA’s 2016 MIST guidance states that phase 2 conjugates are generally pharmacologically inactive, however where a potentially toxic conjugate, such as an acyl glucuronide is formed, additional safety assessments may be needed. Idiosyncratic drug toxicity of carboxylic acid-containing drugs can be caused by the formation of reactive acyl glucuronides,1 which have the ability to directly acylate proteins and undergo intramolecular rearrangement producing reactive aldehydes leading to protein glycation.
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Hypha Discovery is a UK-based CRO supporting pharmaceutical and agrochemical companies worldwide through the production of metabolites and new derivatives of drugs and agrochemicals in discovery and development.