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Nanobodies that neutralize Monoclonal antibodies that bind to the spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) show therapeutic promise but must be produced in mammalian cells and need to be delivered intravenously. By contrast, single-domain antibodies called nanobodies can be produced in bacteria or yeast, and their stability may enable aerosol delivery. Two papers now report nanobodies that bind tightly to spike and efficiently neutralize SARS-CoV-2 in cells. Schoof et al. screened a yeast surface display of synthetic nanobodies and Xiang et al. screened anti-spike nanobodies produced by a llama. Both groups identified highly potent nanobodies that lock the spike protein in an inactive conformation. Multivalent constructs of selected nanobodies achieved even more potent neutralization. Science , this issue p. 1473 , p. 1479

Summary Therapeutic and diagnostic efficacies of small biomolecules and chemical compounds are hampered by suboptimal pharmacokinetics. Here, we developed a repertoire of robust and high-affinity antihuman serum albumin nanobodies (NbHSA) that can be readily fused to small biologics for half-life extension. We characterized the thermostability, binding kinetics, and cross-species reactivity of NbHSAs, mapped their epitopes, and structurally resolved a tetrameric HSA-Nb complex. We parallelly determined the half-lives of a cohort of selected NbHSAs in an HSA mouse model by quantitative proteomics. Compared to short-lived control nanobodies, the half-lives of NbHSAs were drastically prolonged by 771-fold. NbHSAs have distinct and diverse pharmacokinetics, positively correlating with their albumin binding affinities at the endosomal pH. We then generated stable and highly bioactive NbHSA-cytokine fusion constructs “Duraleukin” and demonstrated Duraleukin's high preclinical efficacy for cancer treatment in a melanoma model. This high-quality and versatile Nb toolkit will help tailor drug half-life to specific medical needs., Graphical abstract, Highlights • We provide a resource of high-affinity and versatile albumin nanobodies for drug delivery • We systematically map albumin nanobody epitopes by hybrid structural approaches • We parallelly measure the pharmacokinetics of nanobodies in a humanized mouse model • We develop nanobody-cytokine conjugates “Duraleukin” for cancer immunotherapy, Drug delivery system; Biochemical engineering; Biotechnology; Structural biology; Proteomics

Therapeutic and diagnostic efficacies of numerous small biomolecules and chemical compounds are hampered by poor pharmacokinetics. Here we developed a repertoire of distinct and high-affinity albumin-nanobodies (NbHSA) to facilitate drug delivery. Using biophysics and hybrid structural methods, we have systematically characterized the Nb repertoire, mapped the epitopes, and resolved the architecture of a tetrameric Nb-albumin complex. We employed quantitative proteomics for accurate and multiplex pharmacokinetic analysis of dozens of diverse and high-quality NbHSA and confirmed the most stable construct has a 771-fold T1/2 improvement compared to non-albumin binding Nbs. Interestingly, the pharmacokinetics of NbHSA is related to their biophysical and structural properties. To demonstrate the utility of NbHSA, we developed stable NbHSA-cytokine conjugates “Duraleukins” and confirmed the high anticancer efficacy of a Duraluekin in vivo. This high-quality Nb resource may help advance research into novel biotherapeutics.

Therapeutic and diagnostic efficacies of numerous small biomolecules and chemical compounds are hampered by the short half-lives. Here we report the development of a repertoire of diverse, high-affinity albumin-nanobodies (NbHSA) to facilitate drug delivery. By integrating biophysics, and hybrid structural biology, we have systematically characterized the NbHSAfor albumin binding, mapped the epitopes, and resolved the architecture of a tetrameric Nb-albumin complex. We employed quantitative proteomics for accurate, multiplex Nb pharmacokinetic analysis. Using a humanized albumin mouse model, we found that the NbHSAhas outstanding pharmacokinetics; the most stable NbHSAhas a 771-fold T1/2improvement compared with a control Nb. Interestingly, the pharmacokinetics of NbHSAis related to their biophysical and structural properties. To demonstrate the utility of NbHSA, we developed a highly stable NbHSA-hIL-2 cytokine conjugate “Duraleukin” and confirmed its improved anticancer properties than hIL-2 alone. We envision that this high-quality Nb resource will advance research into novel biotherapeutics.