Merck & Co’s adjuvanted, tetravalent subunit vaccine V180 comprises truncated forms of envelope proteins (DEN-80E), derived from strains of all four dengue virus serotypes (DEN-1 strain 258848, DEN-2 strain PR159 S1, DEN-3 strain CH53489, and DEN-4 strain H241). The DEN-80E subunits are expressed from plasmids in the Drosophila S2 cell expression system and are then formulated with either ISCOMATRIX (saponin, cholesterol, and phospholipid adjuvant; CSL) or Alhydrogel (aluminium hydroxide gel adjuvant; Brenntag Nordic).
V180 is currently in Phase I development in the US and Australia only, but Merck & Co is likely to target the same dengue-endemic Asia-Pacific and Latin American markets as Sanofi Pasteur and Takeda.
V180's more compact dosing schedule could make it a more attractive alternative to Dengvaxia, particularly for travelers, although its current three-dose schedule could still be improved upon to reduce the risk of non-compliance.
The author believes that V180 would achieve its greatest commercial potential as part of a heterologous prime-boost strategy with TetraVax-DV (tetravalent live-attenuated chimeric vaccine; Biological E/Panacea Biotec/Butantan Institute/Merck & Co/Vabiotech), which the company has in-licensed from the US National Institutes of Health, potentially simplifying the vaccination schedule to just two doses. Such a strategy would be attractive for routine immunization programs and for the traveler/military segments, but V180 will likely face competition from GlaxoSmithKline, which is currently pursuing a similar strategy with DPIV (adjuvanted, tetravalent formalin-inactivated vaccine). However, Merck & Co is yet to launch Phase II trials, and since there has been no progress in development since Q4 2016, the future of V180 is unclear.