Onyx is now licensed to manufacture commercial API from our UK facility

Solid State Chemistry

Guiding you through successful drug development with expert solid form screening and selection.

Our Approach

We use solid state chemistry to mitigate risk throughout the development process by gaining an in-depth understanding of the physicochemical properties of your active pharmaceutical ingredient (API).

We take an adaptive and collaborative approach to development, flexing with your needs and working closely with you to help you meet your crucial milestones.

The combined expertise of our leadership group and our dedication to our partnership ensure that the right decisions are made to progress your product from development through to commercialization.

Salt and Co-crystal Screening

In the early stages of your product’s lifecycle, we recommend a thorough performance evaluation of your API to determine whether a salt or co-crystal version is required and developable.

As part of our preformulation activities, we perform in-depth salt screening and a risk/benefit assessment of appropriate versions. This includes identifying biorelevant dissolution and solubility characteristics to help inform your future development strategies.

Polymorphic Screening

Early in the development lifecycle, we can define the ideal polymorphic variant of your API using a robust yet pragmatic screening approach and articulating in detail its available solid state landscape.

Polymorphic screening allows us to map out the characteristics of your molecule, identify potential development challenges and therefore de-risk the  transition from discovery into clinical manufacture and beyond.


In the preformulation stage of your drug development journey, we analyse the characteristics and behaviours of your API to determine its optimal solid state.

We examine the chemical stability, solid state stability, shelf-life and solution behaviour of your chosen version, both in the presence and absence of excipients, enabling us to identify and troubleshoot any solubility-related issues early in the development phase.

Crystallization Development

A critical stage in your drug’s development journey is the study of crystallization and the identification of a purifying recrystallization, or salt forming crystallization.

Our solid state chemistry teams work together to ensure that process-typical material is well defined and its behaviour can be contrasted with that of the pure phase.

We’ll successfully navigate complex solid state challenges and gain a robust understanding of the unique attributes of your molecule, allowing us to ensure that your chosen solid form can be reproduced at scale.

Chiral Resolution Screening

An extension of our solid state chemistry services, our chiral resolution screening enables us to crystallize and isolate your enantiopure API.

Conducted in parallel to screening phases, our well-established approach selects the most efficient processes to enable the straightforward isolation of your bulk enantiopure product.


Across all our screening activities, we endeavor to isolate candidates fit for single crystal structure determination. We also offer a bespoke crystallography service to grow single crystals of your molecule and provide a fully detailed report.

Milling for Oral Solid Dosage (OSD)

Our milling services help prepare your molecule for oral solid dosage (OSD) formulation, allowing you to deliver a product with an improved surface area.

We can offer:

  • Analytical-scale ball milling to aid your pre-formulation assessments
  • Ytron-Quadro Fitz and Comil milling capabilities to remove lumps or reduce the size of your solid form particulates.

All activities are supported by our in-house particle size distribution (PSD) method evaluation to take your molecule from early phase batch profiling to formal method development and validation.


  • “This is certainly the most difficult solid state project I have ever worked on and I did think on occasions it was becoming intractable. Job very well done!”

    Dr. Christopher Wallis, Industry Consultant