The starting point for the study was CD388, a long-acting drug–Fc conjugate that has recently emerged as a new class of antiviral against both influenza A and influenza B. CD388 links a small-molecule inhibitor to the crystallizable fragment of an antibody, extending the drug’s residence time in the body while retaining its ability to bind the viral target. What remained unclear, however, was how exactly the Fc conjugation reshapes the function of the small molecule it carries. The researchers set out to answer that question systematically, and in doing so they uncovered a mechanism that had not been appreciated before.

To do this, the team built a platform based on click chemistry, a family of highly reliable bioconjugation reactions that allow molecular building blocks to be joined in a modular, almost Lego-like fashion. The platform makes it possible to flexibly combine different valencies, meaning different numbers of drug copies, with different conjugated drugs on the same Fc scaffold. Using the neuraminidase inhibitor zanamivir as a model drug, the researchers prepared mono-, di- and trivalent versions, each carrying one, two or three zanamivir molecules attached to the Fc fragment. This controlled series allowed them to interrogate, for the first time in a rigorous way, how valency alone governs antiviral behavior.

The results were striking. The trivalent zanamivir–Fc conjugate, designated AVC-Z3, exhibited higher antiviral activity than the mono- and divalent versions. But the more important discovery was mechanistic. Rather than merely blocking the enzymatic activity of viral neuraminidase more strongly, AVC-Z3 did something physically dramatic: it induced inter-virion aggregation. Because each conjugate carries three zanamivir ligands, a single AVC-Z3 molecule can bind neuraminidase proteins on more than one virus particle at the same time, cross-linking the virions into aggregates. The Fc fragment, with its own multivalent binding capacity, further supports this clustering effect.

This cross-linking produces a dual-stage inhibition that represents a genuine mechanistic shift. In the traditional view, neuraminidase inhibitors such as zanamivir and oseltamivir work by suppressing the enzyme that influenza uses to cleave sialic acid receptors, a step essential for newly formed virions to detach from an infected cell and spread. With AVC-Z3, the blockade of viral entry is coupled to the restriction of viral release. Virions that are cross-linked into aggregates cannot move freely, attach efficiently to new cells, or escape from the surfaces where they are produced. In effect, the drug no longer just disables a viral enzyme; it physically immobilizes the virus particles themselves.

The implications of this shift are considerable. A mechanism based on physical cross-linking is less dependent on the precise chemistry of the neuraminidase active site, which is where most resistance mutations to conventional inhibitors arise. By converting a single-target enzyme inhibitor into a multivalent cross-linking agent, the platform could in principle make it harder for the virus to escape through the usual mutational routes. The authors describe ligand valency as a determinant of antiviral mechanism, a framing that elevates valency from a simple potency knob to a design parameter that controls what kind of antiviral activity a conjugate delivers.

Encouraged by the zanamivir results, the team applied the same logic to a second neuraminidase inhibitor, peramivir. They synthesized a trivalent peramivir–Fc conjugate, AVC-P3, and found that it showed stronger antiviral activity than AVC-Z3 in vitro. Just as importantly, AVC-P3 displayed a much longer half-life in vivo than AVC-Z3 and than CD388 carrying the YTE mutation, an Fc engineering change often used to extend antibody half-life by improving binding to the neonatal Fc receptor. The combination of high potency and long persistence is exactly what is wanted in a long-acting prophylactic or therapeutic agent, particularly for vulnerable populations or outbreak settings where dosing logistics are difficult.

The in vivo performance of AVC-P3 was tested in mouse models of infection with four different influenza challenges: H1N1, H3N2, H5N1 and influenza B. Across all of these models, the efficacy of AVC-P3 surpassed that of the other AVCs, of baloxavir, a cap-dependent endonuclease inhibitor that represents one of the newest classes of influenza drugs, and of CD388 itself. Covering both influenza A subtypes, including the highly pathogenic H5N1, and influenza B in a single agent speaks to the breadth that the neuraminidase-targeting, Fc-conjugated approach can offer. H5N1 remains a pandemic concern given its ongoing circulation in birds and sporadic human infections, so a long-acting agent active against it has obvious strategic value.

The study also carries a broader message for antiviral drug design. Small-molecule antivirals and biologics have traditionally occupied separate worlds, with small molecules prized for potency and manufacturability and antibodies valued for specificity and long half-life. Drug–Fc conjugates blur that boundary, and the present work demonstrates that the design space within that hybrid class is richer than assumed. By making valency programmable, the click-chemistry platform turns the number of drug copies per Fc into an experimentally tunable variable, allowing researchers to map how valency reshapes mechanism, potency and pharmacokinetics. The finding that trivalency unlocks cross-linking suggests that other viral targets with dense surface display of ligands, such as hemagglutinin or surface glycoproteins of unrelated viruses, might be amenable to the same strategy.

Caveats remain, as they always do at this stage. The efficacy data come from mouse models, and the pharmacokinetic advantages observed in animals will need to be confirmed in higher species before the approach can be considered for clinical development. Questions about manufacturing consistency, immunogenicity of the conjugates and the behavior of virion aggregates in the complex environment of the human respiratory tract will all require attention. Nevertheless, the study defines a clear principle: ligand valency is not merely a matter of avidity but a switch that can convert a conventional enzyme inhibitor into a physically immobilizing, dual-stage antiviral. If that principle holds up through further development, the multivalent conjugate platform could offer a durable new line of defense against a virus that has repeatedly shown its capacity to surprise.

Subject of Research: Multivalent drug–Fc conjugates that cross-link influenza virions to enhance antiviral activity

Article Title: Multivalent antiviral conjugates enhance activity against Influenza via cross-linking viruses

Article References: Feng, X., Yuan, L., Zhao, L., Liu, L., Xie, F., Zhou, M., Cheng, G., Guan, Y., Xia, N., Cheng, T., Zhong, W., Xiao, D., Zhou, X., & Li, S. (2026). Multivalent antiviral conjugates enhance activity against Influenza via cross-linking viruses. Nature Communications. https://doi.org/10.1038/s41467-026-78126-3

Image Credits: AI Generated

DOI: 10.1038/s41467-026-78126-3

Keywords: influenza, antivirals, drug–Fc conjugates, multivalency, neuraminidase inhibitors, zanamivir, peramivir, CD388, cross-linking, viral aggregation, H5N1, drug development

Despite considerable progress, most antibody recruiters reported to date suffer from a fundamental weakness: they rely on monovalent interactions at both ends. The small haptens commonly used to bind endogenous antibodies have intrinsically low affinity, and the dense sugar coating on tumor cell membranes, the glycocalyx, further shields these interactions from working efficiently. Polymeric antibody-recruiting systems have been developed to present multiple binding motifs at once, boosting avidity, but they often sacrifice control over how the motifs are spatially arranged and which cells they engage. Nonspecific membrane anchoring and synthetic polymer scaffolds raise additional concerns about off-target effects and biocompatibility, leaving open a central design question: how can small molecules generate a cell-selective, multivalent antibody-binding display without permanent, bulky synthetic scaffolds?

A team reporting in Advanced Science has now answered that question with a strategy borrowed from supramolecular chemistry: receptor-triggered peptide self-assembly. Their approach exploits a principle that biology itself uses everywhere, in which many weak interactions acting in concert become collectively strong. The researchers designed a series of modular peptide conjugates, labeled P1 through P4, each combining three functional modules. The first is GE11, a twelve-amino-acid peptide (sequence YHWYGYTPQNVI) that binds the epidermal growth factor receptor, EGFR, which is overexpressed on many aggressive tumors. The second is dinitrophenyl, or DNP, a classic hapten recognized by anti-DNP antibodies that can be raised or already present in serum. The third is a short self-assembly motif built from diphenylalanine, a dipeptide famous for its tendency to form ordered beta-sheet nanostructures. Polyethylene glycol linkers of varying lengths were inserted to tune solubility and flexibility, and P4, which lacks the diphenylalanine motif, served as a non-assembling control.

The design logic is elegant. In solution, the conjugates exist as discrete monomers. Once the GE11 module docks onto EGFR on a cancer cell membrane, however, the receptor acts as a nucleating scaffold that guides the diphenylalanine motifs to polymerize in situ into extended fibrillar networks. The result is a dense, spatially confined carpet of DNP haptens displayed directly on the tumor cell surface, precisely where they are needed to capture anti-DNP antibodies with high avidity. Transmission electron microscopy confirmed the transformation: P3 alone formed mostly amorphous aggregates, but when incubated with EGFR protein it assembled into extended fibrillar networks, while the control peptide P4 formed no ordered structures under identical conditions. The assembly proved robust across physiologically relevant buffer and pH conditions tested.

The quantitative gains from assembly were striking. On EGFR-overexpressing HeLa cells, P3, which carries a PEG6 spacer identified as the optimal balance between hapten accessibility and receptor anchoring, recruited anti-DNP antibodies with normalized mean fluorescence intensities 4.6-fold and 9.4-fold higher than P4 at concentrations of 10 and 20 micromolar respectively after three hours. Time-course experiments showed recruitment rising rapidly within the first three hours and plateauing by 24 hours, reaching an 11.8-fold advantage over the non-assembling control. Assembly also conferred a survival benefit to the molecule itself: in serum stability assays containing 30 percent fetal bovine serum, P3 retained roughly 28 percent of its initial concentration after eight hours, whereas P4 was completely degraded. The critical aggregation concentration of P3 was measured at 6.5 micromolar, and microscale thermophoresis confirmed that supramolecular modification did not compromise receptor binding, with P3 retaining high affinity for EGFR comparable to the parental GE11 ligand.

Selectivity, the property that determines whether such a therapy can spare healthy tissue, was verified at multiple levels. Competitive experiments showed that free GE11 markedly attenuated antibody recruitment, confirming EGFR dependence. Strong membrane-associated fluorescence appeared on EGFR-positive HeLa, MDA-MB-231, and A549 cancer cells, while EGFR-negative normal human dermal fibroblasts showed only weak signal. Scanning electron microscopy provided the most vivid evidence: untreated cells displayed smooth membranes, but after incubation with P3, HeLa cells were covered in extensive fibrillar networks, while fibroblasts remained entirely free of such assemblies. In excised tumor tissue sections from mice, P3-treated samples showed pronounced antibody accumulation at tumor cell membranes, whereas the non-assembling control induced minimal recruitment.

Crucially, the recruited antibodies were not merely decorative. When cells coated by P3-recruited anti-DNP antibodies were exposed to complement, the EGFR-positive cancer lines underwent lysis ranging from 20.4 to 39.2 percent, while the EGFR-negative fibroblasts showed essentially no lysis, comparable to vehicle controls. P3 also showed no detectable cytotoxicity toward primary human blood cells at concentrations up to 100 micromolar over 24 hours, suggesting that the immune activation is confined to cells bearing the assembled hapten display rather than being an inherent toxicity of the molecule.

The therapeutic promise carried through to animal models. In HeLa xenograft-bearing mice provided with anti-DNP antibodies, P3 administered every two days at 10 milligrams per kilogram suppressed tumor growth dramatically. After two weeks of treatment, mean tumor volume in the P3 group was 264.1 cubic millimeters, compared with 1264.3 cubic millimeters for vehicle-treated animals and 1003.0 cubic millimeters for those receiving the non-assembling control, corresponding to a tumor growth inhibition rate of 79.1 percent versus 20.7 percent. Safety profiling was equally encouraging: body weights, organ weights, liver enzymes, and hematological parameters remained within normal ranges, histology of major organs revealed no inflammatory infiltration or necrosis, and tumor sections from treated mice showed extensive necrotic regions with nuclear condensation, hallmarks of effective cell killing in vivo.

The authors are candid about a limitation that must be solved before clinical translation: P3’s intrinsic tendency to aggregate in the absence of EGFR binding. They propose that molecular engineering of the self-assembly motif, incorporating hydrophilic or stimulus-responsive elements such as phosphatase-responsive phosphate groups or glucose-derived units, could suppress nonspecific aggregation while preserving receptor-triggered assembly. The modular architecture of the design also invites adaptation: swapping GE11 for ligands targeting other tumor receptors, or DNP for alternative haptens, could generate a family of antibody-recruiting therapeutics tailored to different cancers. By converting a monovalent small molecule into a multivalent immune platform through nothing more than a receptor’s own organizing power, the work establishes a general chemical principle that could reshape how synthetic immunotherapies are built, offering a cheaper, more biocompatible alternative to engineered antibody proteins while harnessing the immune system’s existing arsenal.

Subject of Research: Receptor-triggered peptide self-assembly for multivalent recruitment of endogenous antibodies in cancer immunotherapy

Article Title: Receptor‐Triggered Peptide Self‐Assembly Enables Multivalent Recruitment of Endogenous Antibodies for Cancer Immunotherapy

Article References: Wang, Y., Wu, X., Zhao, C., Han, H., Xie, W., Yuan, D., & Shi, J. (2026). Receptor‐Triggered Peptide Self‐Assembly Enables Multivalent Recruitment of Endogenous Antibodies for Cancer Immunotherapy. Advanced Science, Article e78074. https://doi.org/10.1002/advs.78074

Image Credits: AI Generated

DOI: 10.1002/advs.78074

Keywords: cancer immunotherapy, antibody-recruiting molecules, peptide self-assembly, supramolecular chemistry, EGFR, multivalency, complement-dependent cytotoxicity, dinitrophenyl hapten, GE11 peptide, nanofibers, tumor targeting, Advanced Science