Boost stability & immunogenicity
ncAA: β-amino acids
Incorporation molecule: Mucin-1 (MUC1)
Impact: Boost stability & immunogenicity
MUC1 is oncology's priority target—a protein that's cranked up and twisted on the surface of tough foes like breast, ovarian, and pancreatic cancers. Here, a fresh 2025 study flips the script on MUC1-based cancer vaccines by weaving in non-canonical β-amino acids—close cousins to proteogenic α-L-amino acids but with stretched-out backbones that deliver spectacular upgrades. These clever swaps amp up proteolytic stability, letting glycopeptides dodge rapid breakdown in the body for killer bioavailability. Smartly positioned within and outside the key immunodominant epitope, they lock in native shapes and antibody grip, sparking immune responses that match or outshine the originals when hitched to gold nanoparticles—ultimately pumping out more IFNγ cytokines for precision tumor takedowns.
Citation: Gibadullin et al., 2025
Source publicationLearn more about Boost stability & immunogenicityCell permeability
ncAA: β-lactam-lysine
Incorporation molecule: Fibronectin type III monobody
Impact: Cell permeability
For decades we've been told the same story: antibodies are extracellular drugs only. ~90% of the proteome – the real treasure trove of "undruggable" targets – stays forever out of reach behind the plasma membrane. Not anymore. A single, precisely placed non-canonical amino acid can turn a tiny domain antibody (nanobody, monobody, DARPin – you name it) into a cell-penetrating missile that actually works inside living cells.
The group took a fibronectin type III monobody, supercharged it to +18 net charge, genetically encoded a β-lactam-lysine (BeLaK) at the N-terminus, watched it spontaneously form an intramolecular covalent strap with a nearby lysine. The result: spontaneous uptake at only 40 nM, clean endosomal escape, and sub-micromolar inhibition of ERK1/2 phosphorylation in esophageal cancer cells.
Citation: Rabb et al., 2025
Source publicationLearn more about Cell permeabilityNew-to-nature geometries
ncAA: Broad palette
Incorporation molecule: BH3 mimetics
Impact: New-to-nature geometries
Here is a 2025 powerhouse paper that's redefining the fight against Acute Myeloid Leukemia (AML)—a brutal foe notorious for dodging therapies like BCL-2 inhibitors such as Venetoclax. Enter the game-changer: BH3 mimetics (those clever drugs that ape the BH3 domain, a pro-apoptotic α-helical snippet from the BCL-2 family proteins) supercharged with non-canonical amino acids (ncAAs) for dual takedown of MCL-1 and BCL-xL.
Through savvy site-saturation mutagenesis, the team dialed up binding affinities to impressive IC50s of 2.77 nM for MCL-1 and 10.69 nM for BCL-xL—a fourfold leap in potency. This precision fit—nailed by rigid cyclohexyl side chains for unmatched shape complementarity and hydrophobic packing—simply can't be pulled off with the standard 20 amino acids!
Citation: Wang et al., 2025
Source publicationLearn more about New-to-nature geometriesPrecise bioconjugation
ncAA: Azide: AzK
Incorporation molecule: AAV capsid
Impact: Precise bioconjugation
Gene therapy has a simple but serious problem: AAV vectors go where they want to go, not where you want them to go. Most love the liver. Because of this, scientists often push doses very high to force enough vector into the right tissue. That's when toxicity rises, safety drops, and manufacturing costs explode.
Now imagine you could "click" on the exact targeting protein you want, in the exact position, in the exact number of copies—turning a virus into a guided missile for one tissue. Using one ncAA (AzK) at a chosen site in the AAV capsid, this example built designer AAVs decorated with an anti-HER2 nanobody, and even with full-length trastuzumab. The standout result is the HER2-targeted vector: gene delivery to tumours jumps 19x in vivo. This lets us design vectors that hit one cell type with accuracy, reduce dose and improve safety.
Citation: Pham et al., 2025
Source publicationLearn more about Precise bioconjugationMolecule activation
ncAA: L-DOPA
Incorporation molecule: Collagen
Impact: Molecule activation
Most people know L-DOPA as a dopamine precursor used in Parkinson's disease. Mussels add it to proteins after translation, using enzymes that modify tyrosine residues. But L-DOPA has another life — one that biology never fully explored, because it is not a natural protein building block!
Collagen is the backbone of tissues. But natural collagen is slow to produce, hard to tune, and often carries safety risks. When you add L-DOPA into collagen-like scaffolds, you unlock: faster and stronger self-assembly, hydrogel formation, improved adhesion to cells and surfaces; better biocompatibility, enhanced migration and angiogenesis in early studies. By placing L-DOPA exactly where you want it you turn collagen from a passive scaffold into an active, programmable material in a single step.
Citation: Deutschman et al., 2025
Source publicationLearn more about Molecule activationEnhanced catalytic activity
ncAA: Hydrophobic
Incorporation molecule: Bacterial laccase
Impact: Enhanced catalytic activity
Laccases, nature's "green" catalysts, shine in applications like pollutant degradation, biomass valorization, product bleaching, synthetic chemistry, bioremediation, food treatment, and textile processing.
Now, hydrophobic tuning is like adjusting the "greasy" or water-repelling parts of these enzymes. Hydrophobic amino acids have side chains that shun water, helping proteins fold into the right shape or create cozy pockets for chemical reactions. Hydrophobic tuning is the dialing in the right level of "oiliness" to make the enzyme stable, efficient, or interactive—just right for its job. The catch? The 20 canonical amino acids offer only a handful of truly hydrophobic options: mainly leucine, isoleucine, valine, phenylalanine, and methionine. Non-canonical amino acids open up a vast universe of hydrophobic options to unlock precise control of enzyme activity.
Citation: Fischer et al., 2025
Source publicationLearn more about Enhanced catalytic activityComplete biosynthesis
ncAA: pAPhC
Incorporation molecule: SFC enzyme
Impact: Complete biosynthesis
In this technological feat, scientists built a system where E. coli produces and incorporates a new catalytic amino acid — S-(4-aminophenyl)-L-cysteine (pAPhC) — all inside the same cell. No external synthesis. No expensive feeding. Just pure biosynthetic wizardry.
The magic ingredient? A mercapto-aniline group — a catalytic handle never seen in nature — that turns ordinary proteins into true chemical machines. Using this approach, the team created a designer enzyme that performs an enantioselective Friedel–Crafts alkylation (a reaction beloved by organic chemists for building chiral carbon-carbon bonds in pharmaceuticals, agrochemicals and fragrances) with 95% enantiomeric excess and 98% yield. This merges metabolic engineering and genetic code expansion — effectively teaching cells to forge their own xenobiotic chemistry.
Citation: Huang et al., 2025
Source publicationLearn more about Complete biosynthesisProtease resistance
ncAA: β-amino acids
Incorporation molecule: Aurein 1.2
Impact: Protease resistance
The AMR crisis is scary enough with bacteria, but fungal pathogens are a nightmare: >1.5 million deaths/year and rising resistance. We urgently need new weapons! Nature already has one: aurein 1.2, a tiny 13-mer antimicrobial peptide from Australian bell frogs that punches holes in microbial membranes — a mechanism that rarely breeds resistance. Problem? It's rapidly eaten by proteases and too toxic to human cells.
In this work the authors used iterative Gaussian process regression to dive into broad chemical space of 336,000 virtual α/β-peptides derived from aurein 1.2. Result? Brand-new sequences with up to 52-fold higher antifungal selectivity. α/β-peptides are underrepresented in databases compared to their all-α cousins, but this approach uses smart, low-data machine learning to create powerful new designs.
Citation: Chang et al., 2025
Source publicationLearn more about Protease resistanceModular bispecifics
ncAA: Azide: AzK
Incorporation molecule: Nanobodies
Impact: Modular bispecifics
Here we shine a spotlight on one of 2025's most relevant ncAA-driven innovations; a "new-to-nature" superpower that could rewrite how we build bispecific antibodies. Forget DNA fusion tricks — these scientists stitch proteins together exactly where they want!
In a standout preprint from Roman Adomanis et al., Blaise Kimmel Lab, The Ohio State University, researchers used genetically encoded non‑canonical amino acids (ncAAs) to craft modular bispecific nanobodies with fully controlled topology — something conventional protein expression could never achieve. These amino acids don't exist in nature, but once woven into nanobodies, they become perfect chemical anchoring points. As a result: geometry becomes a design variable, potency can be tuned without re-cloning DNA and assembly is fully homogeneous and CMC‑friendly.
Citation: Adomanis et al., 2025
Source publicationLearn more about Modular bispecificsDynamic activity control
ncAA: Photoswitch
Incorporation molecule: Enzymes
Impact: Dynamic activity control
None of the 20 canonical amino-acid side chains contains a built-in photoswitchable chromophore that undergoes clean, reversible light-driven isomerization the way synthetic photoswitches do. Yet, photoswitchable ncAAs play a crucial role in engineering light sensitivity in enzymes. Here, we highlight authors who went on a crusade to expand the photoswitchable ncAA repertoire for the recombinant production of photocontrolled enzymes using azobenzene, arylazopyrazole, arylazothiazole, hemithioindigo, and spiropyran photoswitch scaffolds.
Now let's dream about broader applications of photoswitchable ncAAs: biotherapy with enzymes that activate only where and when you shine light; biocatalysis: light-controlled enzymes could transform drug synthesis and biofuel production. This work pushes ncAAs into dynamic, reversible control.
Citation: Hiefinger et al., 2025
Source publicationLearn more about Dynamic activity controlFine-tuned acid-base switch
ncAA: Histidine-like
Incorporation molecule: Various
Impact: Fine-tuned acid-base switch
Histidine stands apart from all other amino acids for one simple reason: its pKa sits right next to physiological pH. The imidazole side chain shifts between charged and uncharged forms at normal cellular conditions. That makes it the perfect acid–base switch inside proteins. It is why histidine shows up again and again in enzyme active sites.
Here we celebrate work that created 12 histidine-like non-canonical amino acids with systematically tuned properties and cellular machineries for incorporation of these. These span a wide range of nitrogen pKa values and include five alternative heterocycles beyond imidazole. This is not just substitution, but fine control over one of biology's most powerful chemical switches!
Citation: Perdigeuro et al., 2025
Source publicationLearn more about Fine-tuned acid-base switchQuinoline heterocycles
ncAA: β-keto/γ-keto
Incorporation molecule: Peptides
Impact: Quinoline heterocycles
For decades recombinant peptides lacked the chemistry that makes small molecules win. Until now.
Using genetic code expansion, scientists installed β-keto and γ-keto ncAAs at the N-terminus of ribosomally translated peptides, using flexizymes. Then comes the magic: a mild Friedländer reaction that turns those handles into embedded quinoline heterocycles directly on the peptide. Real small-molecule pharmacophores, built by the ribosome. Quinolines form many FDA-approved small-molecule drugs but, until now, were absent from peptides. By encoding kynurenine-type ncAAs, the team drove intramolecular Friedländer macrocyclization, where the quinoline itself becomes the ring-closing element. The result is simple: trillion-member peptide libraries can now start life with real small-molecule pharmacophores already inside them.
Citation: Knudson et al., 2026
Source publicationLearn more about Quinoline heterocyclesHeteropolymer backbone
ncAA: Reactive ester
Incorporation molecule: Various
Impact: Heteropolymer backbone
Adding new chemistry to proteins and peptides is one of the most powerful ideas in synthetic biology. For example, swapping an amide bond for an ester or thioester can unlock new stability, reactivity, or function.
Nature already uses extended backbones. Many natural products contain β-, γ-, or δ-linkages instead of standard α-amino acid bonds. These include drugs and bioactive molecules like taxol, andrimid, actinoramide A, zorbamycin, and pyloricidin D.
Enter BEAR: Backbone Extension by Acyl Rearrangement. In this paper, the authors highlight edit the protein backbone after the protein is made! The researchers designed special hydroxy acids that carry a masked amine nucleophile on the side chain. After the protein is made, the hidden amine gets unmasked and triggers a spontaneous intramolecular rearrangement - altering the backbone after it's created.
Citation: Roe et al., 2025
Source publicationLearn more about Heteropolymer backboneEnhanced ADC linkers
ncAA: Various
Incorporation molecule: Trastuzumab
Impact: Enhanced ADC linkers
Antibody–drug conjugates (ADCs) are a fast-growing class of targeted cancer therapeutics. They combine the precision of monoclonal antibodies with the power of small-molecule cytotoxics. Most approved ADCs rely on the same linker: the protease-cleavable valine–citrulline (Val–Cit) dipeptide. It was designed to release payloads after cleavage by lysosomal cathepsins. In practice, this is a challenge. Val–Cit is cut by proteases in healthy tissues. Payload leaks early. Toxicity follows.
By incorporating ncAAs, the authors of this work identified peptide linkers with high selectivity for cancer-associated proteases. This overcomes the core limitation of conventional linker design. The outcome is clear: potent tumor cell killing; minimal activity from non-cleavable controls and clean separation of on-target versus off-target effects!
Citation: Gorzeń et al., 2025
Source publicationLearn more about Enhanced ADC linkersArchitecture
ncAA: pAcF
Incorporation molecule: Anti-PD-L1 bispecific
Impact: Architecture
Protein engineering usually means swapping one of the 20 amino acids for another and hoping the fold still behaves. ncAAs change the game. They let you add new purposeful chemistry to a protein. A neat example comes from a recent colon cancer immunotherapy paper that uses p-acetylphenylalanine (pAcF) to build an anti–PD-L1 bispecific nanobody with controlled geometry.
Here, by using pAcF to control exactly how two nanobody domains are linked, the authors avoid floppy fusions and wrong orientations. In vivo, this translates into stronger immune activation within the tumour, increased CD8⁺ T-cell infiltration, and delayed tumour growth in colorectal cancer models. Here ncAAs bring control, a new bond type, a defined connection, a reproducible architecture, for properties of homogeneity, stability, affinity, and cleaner translation from bench to manufacturing.
Citation: Hu et al., 2025
Source publicationLearn more about ArchitectureProlonged action
ncAA: Covalent binders
Incorporation molecule: HER2/EGFR bivalent
Impact: Prolonged action
The incorporation of sulfur fluoride exchange (SuFEx) functional groups into protein building blocks is revolutionising protein engineering and therapeutic design by enabling covalent binding of a drug to its target for prolonged activity. However, conventional approaches are challenging, due to limited reactivity and poor site accessibility.
SuFEx-reactive unnatural amino acids—such as fluorosulfate-L-tyrosine (FSY), meta-fluorosulfate-L-tyrosine (mFSY), and fluorosulfonyloxybenzoyl-L-lysine (FSK)—can be site-specifically incorporated into proteins as latent bioreactive building blocks. These aryl fluorosulfate-modified residues remain inert until positioned in close proximity to target nucleophiles (Lys, His, or Tyr) on interacting proteins, enabling precise SuFEx-mediated covalent linkages and increasing tumour retention for drugs.
Citation: Gao et al., 2025
Source publicationLearn more about Prolonged actionCatalysis
ncAA: Noble-metal-binding
Incorporation molecule: LmrR
Impact: Catalysis
For years, artificial metalloenzymes have chased a simple idea: take the best tricks from organometallic catalysis and put them inside a protein. You get selectivity, water compatibility, and evolvability. But noble metals like Au(I) have a problem in proteins: they like soft ligands (think thiolates), and the standard 20 amino acids don't give you the right kind of, well-behaved, genetically placeable soft handle.
These authors use a non-canonical amino acid 4-mercaptophenylalanine (pSHF) — a thiophenol side chain — and install it at a defined site in the LmrR scaffold via Amber-codon suppression. Now the protein contains a purpose-built noble-metal-binding residue that can stabilise low-oxidation-state metals like Au(I), the same oxidation state that does classic π-activation chemistry. This behaves like a fine-tunable gold catalyst from within the protein itself.
Citation: Veen et al., 2024
Source publicationLearn more about CatalysisFunctional switch
ncAA: Phospho mimetic
Incorporation molecule: Small protein
Impact: Functional switch
Phosphorylation controls life. It switches proteins on and off. It tunes signalling, binding, and fate. But it is also kind of messy. Natural phosphotyrosine is unstable. Cells add it and remove it constantly. Purified proteins lose it. Heterogeneity creeps in. Mechanism gets blurred.
This work shows a clean way forward: genetically encoding a new-to-nature phosphotyrosine mimetic directly into proteins. The amino acid is called pentafluorophosphatophenylalanine (PF5CF2Phe). When this ncAA was placed into a small protein scaffold, the result was striking: a protein that strongly inhibits PTP1B and SHP2, two clinically important tyrosine phosphatases – something that was not achieved by the native protein scaffold. This is the key lesson from this paper: the single ncAA flipped the function. ncAAs are not decorations - they are functional switches.
Citation: Ambros et al., 2026
Source publicationLearn more about Functional switchActivity, stability, structure
ncAA: pAzF/AnzL
Incorporation molecule: Endolysins
Impact: Activity, stability, structure
Endolysins are hydrolytic enzymes produced by bacteriophages during the lytic cycle (phage lysins). In practice, they become "enzybiotics" when used therapeutically against bacteria. Despite these advantages, applying endolysins to Gram-negative bacteria and delivering them in patients remains challenging. As protein therapeutics, they also carry familiar liabilities: protease degradation, instability at extreme pH or in serum, poor solubility during recombinant production, and poor oral delivery due to gastric conditions.
In this paper, the authors use genetic code expansion to introduce azido non-canonical amino acids—p-azido-L-phenylalanine (pAzF) and azidonorleucine (AnzL)—at solvent-exposed positions. The swap yields enhanced bacteriolytic activity, superior thermal and storage stability and preserved structural integrity.
Citation: Qi et al., 2025
Source publicationLearn more about Activity, stability, structureStable functional modifications
ncAA: Lysine PTMs
Incorporation molecule: Various
Impact: Stable functional modifications
Lysine acylations sit everywhere in biology. Acetylation. Succinylation. Malonylation. Glutarylation. Itaconylation. Crotonylation. Each one can rewrite a protein's surface. It can change charge. It can change shape. It can change who binds, what falls off, and what the protein actually does.
In this work scientists introduced MeOK into a protein: a landing pad for modifications via a masked hydroxylamine handle. From one MeOK-bearing precursor, they build a whole panel of lysine modifications. In ubiquitin alone, they install eleven distinct PTMs. That includes those that have stayed out of reach for direct encoding: malonylation, succinylation, glutarylation, and itaconylation, plus bulky or reactive motifs. They show impact: like how acetylation of E. coli isocitrate dehydrogenase at K242 reduces catalytic performance, and the effect matches a directly encoded acetyl-lysine control.
Citation: Knecht et al., 2025
Source publicationLearn more about Stable functional modificationsDe novo protein synthesis study
ncAA: ANL
Incorporation molecule: Many
Impact: De novo protein synthesis study
Imagine watching cells rewrite their proteome live, protein by protein. That's the power of BONCAT (bioorthogonal non-canonical amino acid tagging). Using azidonorleucine (ANL), researchers can label newly synthesized proteins and track de novo protein production as it happens—turning the invisible machinery of life into something we can see, measure, and understand.
One of the most compelling applications of ncAA technology reveals how oxytocin can reverse cancer cachexia—the devastating muscle wasting that affects up to 80% of advanced cancer patients and resists conventional nutrition interventions. Using BONCAT, scientists discovered that cancer shuts down de novo protein synthesis in skeletal muscle. But oxytocin flips the switch.
Citation: Sviercovich et al., 2025
Source publicationLearn more about De novo protein synthesis studySelectivity, PK, activation
ncAA: Various
Incorporation molecule: IL-4
Impact: Selectivity, PK, activation
IL-4 is a pivotal cytokine in type 2 immune responses, influencing T cell differentiation, antibody class switching, and macrophage activation. Traditional recombinant engineering limits precise tailoring of IL-4. Cytokines need better pharmacology and new-to-nature features!
Highlight: ncAAs introduce groups conferring novel capabilities like receptor selectivity, conditional activation, and enhanced pharmacokinetics, inaccessible via the genetic code. Homoserine at ligation junctions (Thr37Hse, Met76Hse) acts as benign surrogates, maintaining integrity while enabling efficient amide formation. Norleucine replaces methionines to prevent oxidation. Ornithine at position 116 allows targeted modulation of immune cell responses. PEGylation at a nearby serine (S113Orn) yielded the inverse selectivity.
Citation: Ninomiya et al., 2025
Source publicationLearn more about Selectivity, PK, activationSuperior activity and low tox
ncAA: Halogenated
Incorporation molecule: WK₂
Impact: Superior activity and low tox
Halogens — fluorine, chlorine, bromine, iodine — are workhorses of medicinal chemistry. They tune molecules with precision that carbon, hydrogen, nitrogen, and oxygen alone cannot. Non-canonical amino acids (ncAAs) let us bring those tools into proteins and peptides.
Halogenated ncAAs increase metabolic stability, tune hydrophobicity without bulk, modulate secondary structure, and improve target engagement.
Here we highlight an exciting breakthrough in antimicrobial peptides! Researchers modified WK₂ with fluorinated non-canonical amino acids (like Fup) to create FuK, boosting serum stability from 225 min to over 1440 min. Outcomes: superior antibacterial activity against MDR bacteria, low toxicity, and strong in vivo efficacy for infections.
Citation: Ouyang et al., 2025
Source publicationLearn more about Superior activity and low toxStability, binding
ncAA: Aib/αMeL
Incorporation molecule: GIP-like peptide
Impact: Stability, binding
In December 2025, Eli Lilly shared topline Phase 3 results from TRIUMPH-4 for retatrutide, a first-in-class triple agonist of GLP-1, GIP, and glucagon receptors. Over 68 weeks, people with obesity or overweight plus knee osteoarthritis lost up to 71.2 lb (≈28.7% of body weight), with meaningful drops in osteoarthritis pain and better physical function.
Retatrutide is a 39-mer peptide built mainly on a GIP-like scaffold, tuned to engage all three receptors. A C20 fatty diacid is attached to Lys17 (via a linker) to extend half-life. In the core sequence, Lilly inserted: Aib (α-aminoisobutyric acid) at positions 2 and 20 lock in helical geometry and confer resistance to DPP-4 proteases; αMeL (α-methyl-L-leucine; "α-methylleucine") at position 13 strengthens hydrophobic contacts. These modifications transform a simple peptide into a life-changing drug.
Citation: Lilly release, 2025
Source publicationLearn more about Stability, binding