If you want to assess whether or not any adverse events observed in the clinical trials and/or in practice are related to the treatment, not only other clinical data but also preclinical data can help greatly with assessing causality of the events.
It is important to discuss the coherence (congruence) with other evidence, especially from laboratory experiments: i.e. pharmacological tests and toxicity tests. Search for similar findings as observed in humans in the safety pharmacological tests and in the acute to chronic toxicity tests. If you find any, compare the area under the curve (AUC) values for active ingredient (preferably the unbound drug) between the animal and human. If they are close, it suggests that the adverse event observed in humans is associated with the drug. Be aware that pharmaceutical companies generally do not want to disclose critically important data for assessing risks. So ask for those important data whenever you can and search the web sites of regulatory agencies such as that of the FDA.