The protease inhibitor nelfinavir was used successfully to resensitize patients with proteasome inhibitor–refractory multiple myeloma for proteasome-inhibitor treatment, Dr. Christoph Driessen of Kantonsspital St. Gallen (Switzerland) and colleagues reported in Haematologica.
The researchers had hypothesized that nelfinavir would induce the unfolded protein response and would overcome proteasome-inhibitor resistance. The researchers determined a nelfinavir dose of 2,500 mg twice daily based on a dose-finding study in 12 patients with advanced hematologic malignancies.
Courtesy Wikimedia Commons/KGH/Creative Commons License
In an exploratory extension cohort trial that followed, six patients with relapsed, bortezomib-refractory, lenalidomide-resistant myeloma were treated with 2,500 mg of nelfinavir twice daily in combination with bortezomib; three reached a partial response, two had a minor response, and one had progressive disease. All began the investigational therapy less than 2 months after progressing under therapies with bortezomib/bendamustine/dexamethasone, bortezomib/bendamustine, or bortezomib monotherapy, respectively, the researchers said (Haematologica March 2016;101:346-55).
The study protocol did not allow dexamethasone co-administration until completion of cycle three, when patients who did not achieve a minor response were allowed to co-administer 8 mg dexamethasone with bortezomib. Higher doses were excluded because of potential interactions with nelfinavir through the Cyp3A4 system.
Future research should assess whether bortezomib may be replaced by next-generation drugs like carfilzomib to avoid drug interactions and improve activity and whether nelfinavir may likewise be used in combination with novel oral proteasome inhibitors to boost their low single agent activity. “This ultimately suggests exploring the addition of HIV protease inhibitors to established combinations of proteasome inhibitors with immunomodulatory drugs, for example, in the carfilzomib/lenalidomide/dexamethasone regimen, one of the most powerful and tolerable regimens available to date for advanced multiple myeloma,” they concluded.
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