Cyclic Peptide Design (Head-to-Tail)

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Overview

Head-to-tail cyclisation removes the charged termini that proteases and clearance mechanisms exploit, and it restricts the conformational ensemble so that less binding entropy is lost. Both effects are worth having, and both depend on getting the ring size and the sequence right. We design cyclic peptides against a target site, sample the accessible ring conformations properly, model the complex, and assess the permeability that cyclic peptides may — but frequently do not — achieve.

Schematic: substitutions are scored at every position for stability and function, with catalytic and binding residues protected from redesign.

Key Advantages

Ring Conformations Sampled, Not Assumed

Cyclic peptides occupy a restricted but still substantial conformational space; we generate ensembles and assess the population of the bioactive conformation rather than modelling a single ring.

Cyclisation Chemistry Chosen Deliberately

Head-to-tail, side-chain-to-tail, disulfide and thioether strategies are compared for the sequence in question, since the chemistry affects both stability and achievable geometry.

Permeability Predicted For The Right Chemical Space

Assessment uses models developed for beyond-rule-of-five macrocyclic space, including intramolecular hydrogen bonding and conformational shielding.

Stability Gains Quantified

Predicted protease resistance is compared with the linear parent so the benefit of cyclisation is stated rather than assumed.

Where This Service Is Used

Improving protease stability and half-life of a linear peptide lead

Constraining a bioactive conformation to improve binding affinity

Designing cyclic peptides against extended protein–protein interfaces

Exploring oral or cell-permeable peptide therapeutics

Designing libraries for mRNA or phage display with cyclisation built in

Methods and Techniques Applied

Analysis of the linear parent or the target site to define the cyclisation strategy

Ring size and closure position scanning with strain and geometry assessment

Conformational ensemble generation with enhanced sampling for the cyclic backbone

Complex modelling with the target and assessment of bioactive conformation population

Molecular dynamics of the complex to test stability and the persistence of key contacts

Permeability and property prediction using macrocycle-appropriate models

What We Need From You

Target structure and site, or the linear peptide sequence to be cyclised

Any known bioactive conformation or SAR data from the linear series

Required properties: stability, permeability, route of administration

Available cyclisation chemistry and synthesis constraints

What You Receive

Designed cyclic sequences with the cyclisation chemistry and ring size specified

Conformational ensembles with bioactive conformation population estimates

Complex models with interaction analysis

Predicted stability, solubility and permeability profiles

Synthesis notes and a prioritised testing plan

What We Compute and Report

Ring conformational ensembles with the population of the bioactive conformation

Ring strain and closure energetics per cyclisation position considered

Complex models with interaction analysis for the bound conformation

Permeability estimates computed with macrocycle-appropriate models

Predicted protease resistance compared against the linear parent

Interpretation and Limitations

Computational predictions prioritise hypotheses; they do not independently establish binding, biological activity, therapeutic efficacy, safety or clinical validity. Performance depends on input quality, target class, the structural evidence available and the applicability domain of the selected methods. Scores used for ranking are comparative devices and should not be read as measured quantities. All deliverables are for research use only and are not intended for diagnostic or therapeutic use.

Specifications

Item	Specification	Notes
Ring size	4–20 residues	Larger macrocycles handled as macrocycle design
Designs delivered	15–50 sequences	Spanning ring sizes and closure positions
Typical turnaround	4–7 weeks	Conformational sampling dominates the timeline
Chemistries	Head-to-tail, side chain, disulfide, thioether	Selected per sequence

Service Workflow

Step 01

Scientific Consultation

We discuss the objective, the decision it supports and the data you hold. Nothing is quoted before we understand what the result has to answer.

Step 02

Feasibility Review

We check that the data, target class and available structural evidence can support the proposed approach, and say plainly where they cannot.

Step 03

Technical Proposal

Scope, methods, deliverables, timeline and price are confirmed in writing, together with the limitations we expect to report.

Step 04

Computation and QC

The analysis runs on pinned tool versions in a containerised environment, with quality checkpoints and method comparison where that is informative.

Step 05

Report and Follow-Up

You receive the ranked results, the documented methods, the limitations and a proposed validation plan, plus support in interpreting them.

Is This the Right Service for You?

Choose this service when

A linear peptide lead is cleared or degraded too quickly

Constraining the conformation could recover binding entropy

Oral or cell-permeable peptide chemistry is the objective

Consider another service when

The bioactive conformation is a defined helix

Stapled & Constrained Peptide Design

Non-peptidic chemistry would suit the target better

Macrocycle Design

What Goes Wrong, and How We Handle It

The failure modes that produce confident-looking results which do not survive the next experiment. Each one is designed against rather than discovered afterwards.

Enhanced sampling generates ensembles, and the population of the bioactive conformation is quantified rather than assumed.

Case Studies

The situation

A linear 11-mer bound well but had a plasma half-life of minutes, and the team had no basis for choosing a cyclisation point.

What the work involved

Every closure position was enumerated, ring strain and geometry were assessed, ensembles were generated for the viable options, and the population of the bound conformation was computed for each.

What came back

Two closure positions retained the bioactive conformation as a dominant state; three others distorted the binding face. Six designs were delivered with predicted stability gain and permeability risk for each.

Illustrative of the shape this work takes. Details are generalised, no client or target is identified, and scope and outcome vary with the system in question.

Questions We Are Asked Before Scoping

Note: ICDMO delivers computational (in silico) services. Results prioritise hypotheses for testing; they do not by themselves establish binding, biological activity, efficacy or safety. All deliverables are for research use only and are not intended for diagnostic or therapeutic use. Downstream experimental work is scoped separately and executed through qualified partners.

Get in Touch
about Cyclic Peptide Design (Head-to-Tail)

Tell us about the target, the data you hold and the decision the result needs to support. A scientist reviews every enquiry and replies within one business day.

Feasibility reviewed before any scope or price is fixed

Methods, parameters, confidence and limitations in every report

Confidentiality agreement available before data is shared