Solid Form Screening

The solid form selected for an active pharmaceutical ingredient can influence solubility, dissolution, stability, manufacturability and downstream process development. At Cambrex, we provide phase-appropriate solid form screening to identify and characterize potential forms, evaluate their developability and understand solid-state risks before they affect later development.

At our Edinburgh facility, dedicated solid-state chemistry laboratories support polymorph, salt, co-crystal and broader solid-form investigations, with screening integrated with solid-state characterization and downstream crystallization process development.

Solid Form Screening for Phase-Appropriate API Development 

APIs can exist in multiple crystalline or amorphous forms, including polymorphs, salts, co-crystals, hydrates and solvates. These forms can have different physicochemical properties and different implications for development, processing, and storage.

We design solid form screening programs around the molecule, development phase, available material and program requirements. Studies are structured to:

  • Define the solid-form landscape and relationships between forms
  • Identify stable and metastable forms
  • Evaluate developability using solid-state characterization, solubility and physical and chemical stability data
  • Assess risks such as form conversion during processing or storage
  • Generate evidence-based recommendations for form selection and subsequent development

The objective is not simply to identify additional forms. It is to develop the solid-state understanding needed to select an appropriate form and anticipate the risks involved in advancing it.

Polymorph Screening 

Understand Crystalline Diversity and Identify Forms Suitable for Development 

Polymorphism can affect both API performance and manufacturability. Our polymorph screening studies investigate the crystalline landscape of an API to identify forms suitable for development while detecting alternative forms that could create risks during isolation, processing or storage.

Programs can investigate:

  • Anhydrates, hydrates and solvates within a complex polymorphic landscape
  • Propensity for solvate or hydrate formation
  • Relationships between hydrated and anhydrous forms
  • Relative stability of relevant forms
  • Solubility and physical and chemical stability
  • Potential form conversion
  • Scale-up and developability of selected forms

Experimental approaches include broad crystallization screening across solvents and conditions, amorphization studies, competitive slurry experiments and structural confirmation using techniques including single-crystal X-ray diffraction or electron diffraction.

This understanding supports selection of a developable form while identifying solid-state behavior that may require additional control during crystallization, isolation, handling or storage.

Salt Screening 

Evaluate Salt Forms to Improve API Physicochemical Properties 

Salt formation can be used to modify properties including solubility, dissolution rate, melting point, hygroscopicity, and physicochemical stability. Our rational approach to salt screening considers factors including pKa, intended route of administration and safety when selecting potential acidic or basic counterions.

Salt screening programs can include:

  • Targeted solubility studies
  • Evaluation of pharmaceutically suitable counterions
  • Screening across different crystallization conditions
  • Investigation of potential salt polymorphism
  • Evaluation of crystallization behavior and solid-state properties
  • Scale-up and developability assessment of selected forms

The extent of screening can be adapted to development phase and program objectives, from identifying a viable salt during earlier development to broader investigations that support later-stage development and intellectual property strategy.

Co-Crystal Screening 

Explore Alternative Forms While Retaining the API’s Molecular Identity 

Co-crystals provide another route for modifying the physicochemical properties of an API without changing the chemical structure of the active ingredient. Appropriate pharmaceutically acceptable co-formers may provide opportunities to modify properties such as solubility, stability and bioavailability.

Our co-crystal screening programs can incorporate:

  • Experimental and informatics-based co-former selection
  • Solution and solid-state screening
  • Structural characterization and confirmation
  • Evaluation of stability and solubility
  • Assessment of scalability

The resulting data help determine whether a co-crystal offers a viable development option and how candidate forms compare with other solid-form strategies.

Solid-State Characterization to Support Form Selection 

Solid form selection depends on understanding not only which forms can be generated, but also how those forms differ and behave.

We support screening programs with a range of solid-state characterization capabilities, including:

  • X-ray powder diffraction (XRPD)
  • Variable-temperature and variable-humidity XRPD
  • Thermogravimetric analysis and differential scanning calorimetry
  • Solid- and solution-state NMR
  • Infrared spectroscopy
  • Dynamic vapor sorption
  • Karl Fischer analysis
  • Single-crystal X-ray diffraction and electron diffraction
  • Polarized light microscopy and hot-stage microscopy
  • Particle-size analysis
  • Scanning electron microscopy
  • Gas chromatography

Our Edinburgh team can also support crystallization screening for challenging molecules, chiral resolution screening, peptide crystallization screening, high-throughput screening for process design, amorphous solid dispersion screening and investigative powder-property analysis where required.

From Solid Form Selection to Crystallization Process Development 

Solid form screening establishes the knowledge needed to select a target form. The next challenge is developing a process that reproducibly generates that form with appropriate material attributes.

By integrating solid-form screening with crystallization process development, we can apply knowledge generated during screening to decisions around:

  • Target form selection
  • Particle size, morphology and physical properties
  • Impurity rejection and purity
  • Crystallization parameters
  • Process reproducibility and scalability

This connection between screening and process development helps translate solid-state understanding into the practical controls needed for subsequent scale-up and manufacturing.

Solid-State Expertise in Edinburgh 

We perform solid form screening at our Edinburgh, UK facility, where dedicated laboratories support solid-form screening, characterization and crystallization development.

The team can also support compounds requiring specialized handling and containment, including highly potent APIs, extending our solid-form screening capabilities to programs where occupational exposure considerations affect how development work is performed.

Our Edinburgh facility supports solid-form screening and characterization, small-molecule and peptide crystallization, analytical method development, controlled crystallization reactors, process analytical technology (PAT) and design of experiments (DoE).

Projects are supported by our scientists responsible for study design, data interpretation, solid-form screening and crystallization process development, providing continuity between experimental screening and recommendations for subsequent development.