Are you sure you need an acute study? European pharmaceutical companies have demonstrated that these studies are not needed prior to first clinical trials in humans (Robinson et al. A European pharmaceutical company initiative challenging the regulatory requirement for acute toxicity studies in pharmaceutical drug development. Regul Toxicol Pharmacol. 2008 Apr;50(3):345-52.)
I was part of this initiative cited by Sebastian Hoffmann and I would agree that these studies are not need anymore. There is plenty of high-dose preclinical data being generated during early durg devolopment process that is more than sufficient.