Speed and need: twin development challenges in rapid response for a SARS-CoV-2 antibody cocktail.

Neutralizing antibodies are one available tool for the treatment of infectious diseases. Speed in developing monoclonal antibody treatments is an understood requirement for emerging infectious diseases, and need for COVID-19 treatments during the worldwide pandemic has provided additional urgency. Process development (at Regeneron) and technology transfer (within Regeneron and to Genentech) of casirivimab and imdevimab (REGEN-COV™ or Ronapreve™) manufacturing processes have addressed speed and need with selected purification and cell culture examples provided, respectively, for these two development challenges. This was achieved through three key pillars: (1) Regeneron's proprietary Velocisuite® technologies, (2) deep monoclonal antibody process and manufacturing knowledge at both companies, and (3) Regeneron's and Genentech's commitment to deliver therapeutics to patients in need. Combined with business processes and risk management, these pillars rapidly allowed casirivimab and imdevimab to move to clinical manufacturing and to production at Genentech in a first-time process transfer under compressed timelines between the companies.

The role of the local environment of engineered Tyr to Trp substitutions for probing the denaturation mechanism of FIS.

Factor for inversion stimulation (FIS), a 98-residue homodimeric protein, does not contain tryptophan (Trp) residues but has four tyrosine (Tyr) residues located at positions 38, 51, 69, and 95. The equilibrium denaturation of a P61A mutant of FIS appears to occur via a three-state (N(2) ⇆ I(2) ⇆ 2U) process involving a dimeric intermediate (I(2)). Although it was suggested that this intermediate had a denatured C-terminus, direct evidence was lacking. Therefore, three FIS double mutants, P61A/Y38W, P61A/Y69W, and P61A/Y95W were made, and their denaturation was monitored by circular dichroism and Trp fluorescence. Surprisingly, the P61A/Y38W mutant best monitored the N(2) ⇆ I(2) transition, even though Trp38 is buried within the dimer removed from the C-terminus. In addition, although Trp69 is located on the protein surface, the P61A/Y69W FIS mutant exhibited clearly biphasic denaturation curves. In contrast, P61A/Y95W FIS was the least effective in decoupling the two transitions, exhibiting a monophasic fluorescence transition with modest concentration-dependence. When considering the local environment of the Trp residues and the effect of each mutation on protein stability, these results not only confirm that P61A FIS denatures via a dimeric intermediate involving a disrupted C-terminus but also suggest the occurrence of conformational changes near Tyr38. Thus, the P61A mutation appears to compromise the denaturation cooperativity of FIS by failing to propagate stability to those regions involved mostly in intramolecular interactions. Furthermore, our results highlight the challenge of anticipating the optimal location to engineer a Trp residue for investigating the denaturation mechanism of even small proteins.