GHR and acromegaly: However, current drugs, like the GHR antagonist Pegvisomant®, only inhibit GHR activity when expressed at the outer cell surface by competition with GH binding [6] and are used to mitigate the effects of acromegaly [13], whereas co-expression of GH and the GHR in cancer cells may result in intracellular autocrine activation that will not be inhibited by classic GHR antagonists [2].