Bayer has a patent in the United States on testosterone undecanoate, which it sells under the brand name Aveed. Because it's under patent it charges a high price and Test U is not much used in the US. Custopharm, a generic pharmaceutical manufacturer challenged the patent for obviousness, but lost in a US court, and the decision was recently upheld on appeal.. A news article explains the reasoning in the decision. Personally, I don't agree with the decision and can't see why such a minor point would make Test U patentable.
Custopharm referred to three scientific articles, published before 2003, which describe small clinical studies relating to injectable therapies. The articles inherently disclose benzyl benzoate and castor oil as co-solvents, Custopharm claimed, thereby rendering Bayer’s patents obvious. Each vial of Aveed contains testosterone undecanoate solution in a mixture of benzyl benzoate and castor oil, which act as co-solvents. In 2016, the Delaware court held that Custopharm had failed to demonstrate that the patents were invalid as obvious. The court said that the prior art did not disclose the injection dosage and that Custopharm did not show that a person skilled in the art would have been motivated to lower the dosage found in the articles to the one disclosed in the Aveed patents. Also, the articles did not disclose the injection schedule and did not disclose benzyl benzoate as a co-solvent, the court said. Inherency only arises if it is the “natural result” of the prior art, and Custopharm failed to prove this to be the case here.