One of the main concerns with Aspen is their high intangible asset level on the balance sheet. An intangible asset is an asset that is not physical in nature and includes things like trademarks, patents and goodwill. This often means that the valuation is somewhat subjective.
I did some digging to see how Aspen's level of intangible assets to its total assets compares to other companies in the sector. It made for some interesting reading. Aspen's intangible assets to total assets sits at 57%, GSK sits at 40%, AstraZeneca at 60% and Novartis at 46%. I chose these businesses because Aspen is doing deals with all of them.
I think this ratio does represent the maturity of the business as well as the business's model (R&D or buying established brands). What it certainly makes clear is that these businesses have high levels of intangible assets because of the value of patents and brands within a highly regulated sector. Aspen's current level does not make me feel uncomfortable.