The characterization and application of tamoxifen taste masked beads in preclinical research

Richard’s project, in collaboration with the biotechnology company Fluid Pharma, will facilitate the adoption of a palatable tamoxifen diet at the Cancer Research UK Cambridge Institute. Tamoxifen is commonly used to control spatial and temporal gene expression in studies using transgenic mice. Rodent diet containing tamoxifen is commercially available, but its bitter taste means that it is not readily consumed by mice and this can lead to weight loss as well inter-animal variability in the data obtained and subsequent issues with reproducibility of the studies. Consequently, tamoxifen is often administered by oral gavage or by subcutaneous or intraperitoneal injection. With previous NC3Rs CRACK IT funding, Fluid Pharma have developed micropellets layered with tamoxifen and encapsulated in a taste-masking coating that allows the drug to be added to the rodent diet without changing its palatability. Collaborators at The Mary Lyon Centre at MRC Harwell have worked closely with Fluid Pharma to assess food intake and the dose efficiency of the tasteless tamoxifen diet, demonstrating the welfare and scientific benefits of this innovative product. The award to Richard, the core facility manager at the Cancer Research UK Cambridge Institute, will now enable labs at the Institute to use the diet, helping to build confidence in the utility of this alternative approach for administering tamoxifen. Implementation of the refinement at the Institute will directly benefit more than 4,000 mice over the next three years.

Tamoxifen (TAM) is widely used as a powerful approach to achieve conditional gene knockout (alteration) in mice by inducing temporal and spatial gene expression or deletion using Cre/loxP models. Standard administration protocols for TAM involve repeat dosing by Intra-Peritoneal (IP) injection or Oral Gavage (OG) over several days, both of which are invasive and have the potential to cause pain and stress in experimental animals. The oral feed route is also challenging due to poor palatability of TAM, causing food aversion. Mice dosed with TAM using traditional methods experience marked weight loss 
during the dosing period, leading to risk of morbidity in animals. Additionally, TAM’s limited solubility in dose vehicles complicates dose preparation, resulting in inconsistency and poor reproducibility of experimental results.

Fluid Pharma, a UK biotech, have developed a highly palatable and easy-to-administer oral feed formulation of TAM, comprising drug coated micro-pellets. Preliminary data from this new product have demonstrated that there is no apparent weight loss in animals administered at effective dose of TAM via the feed route and that similar gene recombination efficiency can be obtained when compared to an equivalent OG dosing regimen.

Fluid Pharma aims to establish partnership with a new user, CRUK Cambridge Institute (CRUK CI) to implement the product in their laboratories and to further validate that it is fit-for-purpose for wider adoption. CRUK CI use TAM induced gene expression routinely in the study of cancer and are very familiar with the challenges of TAM administration. The Institute operates with an infrastructure of independent core facilities, bringing together technical specialists
from different scientific disciplines to support the academic research groups. This has resulted in a proven track record to deliver grant-funded innovation projects, making the CRUK CI ideal for this partnership.

In this proposal, CRUK CI will conduct a series of stepwise experiments to achieve the following scientific objectives, for research groups to have the confidence to adopt this new technology: 

• Standardisation of feed administration protocols for practical bead use in a preclinical animal unit
• Product characterisation through investigation of the TAM pharmacokinetics (blood concentrations) when delivered in feed, providing evidence that the beads are delivering adequate and reproducible TAM exposure to mice
• Validation of gene regulation using the palatable TAM beads via oral feed

The project is driven by an urgent 3Rs need in preclinical research and aims to achieve immediate and wider, long term 3Rs impact. In the last 3 years, there have been over four thousand IP injections of TAM to mice at the CRUK CI. A successful validation of this new technology would have the immediate Refinement impact of reducing the number of IP injections and associated stress to the animals. In the longer term, fewer animal interventions and adverse effects associated with TAM administration have the potential to result in higher quality data outputs and a Reduction in animal numbers used. The wider impact would be the adoption of this technology both nationally and internationally in preclinical research. A new product proven to deliver a similar TAM induction effect to the more traditional routes of administration has the potential to result in very significant 3Rs benefits.