@mejefferson I believe that there will soon be an alternative to both human and animal test subjects. Our technology has led us to the artificial growth and sustainability of organs outside of the body. With the maturation of this technology, I believe that there will be a level of observation that we will be able to complete before any drugs reach human/animal organs.

While I have not personally worked on a team partaking in either pre-clinical or clinical research, through doing individual research I have surmised a few reasons as to why failure at the various stages would occur. One of the first reasons I came across was simply not having the resources to complete the research effort, in the form of time or financial constraints. Shipment of necessary equipment in order to carry out the research could also have been delayed, thereby stunting the progression of the project. Like in project management when the initiating phase is overlooked or glossed over, a pre-clinical or clinical research team can erroneous design the study, and modifications could come all but too late. An alternative to abandoning a project altogether could be to pivot and tackle a related research area given what you have, so as to not waste all that was poured into the research effort.

I have yet to work in any type of pre-clinical/clinical research setting and am not sure if/when I would be, but the idea of a failure in this setting doesn't seem daunting. Failure is a part of learning, and science is just continuous trial and error in an attempt to learn something new. The only kinds of failures that would concern me are ones that could've been avoided through proper procedures and protocol, especially with regards to the safety of those involved.

I have have not in vivo experiments with cell cultures and lots of things can go wrong. When i first did cell culture, I stressed to make sure that I was sterilized and I put the right medium for the cells. I also had to make sure everything was room temperature. I also extracted DNA, and performed PCR. In one instance. I accidentally put a used pipette into an expensive substance used for the DNA column, contaminating it. We could not achieve the results because we were working with expired materials. Pre-clinical research is very tedious and about trial and error because there are a lot of procedures and methods that are done to produce a result.

For my career, I have assisted in technical and engineering runs for clients that were going into clinical runs for their processes. For my career, we are working with those who have different types of cancers and we alter their blood to be used as a treatment. For some of the clinical processes that I ended being enlisted in, I have seen some go to commercial production and some have failed after multiple clinical runs. From what I had seen was that the ones that failed tended to not fully anticipated the cells of more sickly patients and how they would interact or be able to handle the stresses of certain pieces of equipment, vectors, ect. I also think that some of them seemed to fail due to lack of research or data on if some patients were already exposed to other CAR T treatments or how certain cancers would interact with CRISPR techniques. 

Since these trials are to either create a more patient-specific treatment or a more generic treatment, I definitely feel that a lot of the larger companies have more success getting past the clinical trials than smaller companies due to multiple factors such as money, time, ect. Since a lot of researchers mostly do these studies on a smaller scale and it does well there, they tend to think upscaling will be able the same but changing dilution factors, wash cycles and taking into account the external stressors on the cells are sometimes not thought of until they get to these clinical and engineering trials. 

Budget constraints are a significant drawback for the failure of preclinical results. The majority of money sanctioned for the project is utilized in preclinical studies. Another reason is the government policies for drugs and medical devices that do not look adequately at preclinical trials. Other reasons for failure can be how the institutional ethical board views the results and acceptability by academia.
Technical failures commonly occur due to a lack of pharmacovigilance, funding, time constraints, wrong assumptions, and study design.

@rd389 I can only imagine how terrifying that must have been. Was the overdose the result of poor GLP or a technician error? Was a study plan written and received by a Study Director? It seems like this incident could have been avoided. How often were the monkeys observed? Did they show signs of overdose? Incidents such as this is why animal testing is debated and deem unnecessary. If I was conducting this study, I would have assigned study numbers to each monkey. There would be an technician on call to observe the animals behavior. I would require good documenting practices and require written evidence of each meal, medicine intake, and other observations such as sleep patterns, appetite, and vitals. I would ensure that the monkeys are being treated well.