top of page

Solid Form Screening and Selection

The majority of drugs are administered as solids.  It infers that apart from the molecular structure of the active ingredient, solid-state properties can significantly influence the performance of the final product.  Often new substances with pharmaceutical activity are weak acids or bases or may have suboptimal solid-state properties.  In such cases it may be preferable to develop the drug as a salt or co-crystal form.  When only amorphous form is known, specially designed crystallization screenings can help to find crystalline candidates, often improving the chemical purity and stability.  General solid form screening (polymorph screening, salt screening, cocrystal screening, crystallization screening, and selection of a desired solid form) strategies that we use at Seven Star are depicted in Scheme-1.

Scheme-1.tif

Scheme 1.  Solid form screening strategies and selection of a desired form for a given API. 

Selection of the best available crystalline candidate should be based on the following physical and chemical parameters:

 

  • Stability (chemical and physical)

  • Solubility/dissolution/bioavailability

  • Hygroscopicity

  • Melting point

  • Polymorph landscape complexity and polymorphic transformations

  • Number of polymorphs

  • Processability

  • Ease of preparation

In addition to its impact on chemical and physical properties, salt and co-crystal formation is also relevant for intellectual property considerations because solids with superior properties can be patent protected.


For the best overall results, Seven Star provides an integrated and comprehensive approach to solid-state development - from systematic salt, co-crystal, and polymorph screening to controlled scale-up of the crystallization process, all complemented with the full range of physicochemical studies performed at Seven Star.

Instrumentation

Aeris X-ray Powder Diffractometer

Empyrean XRPD instrument at Seven Star Pharma
Aeris benchtop XRD instrument at Seven Star Pharma

Empyrean X-ray Powder Diffractometer    

Single crystal X-ray diffraction (SCXRD) instrument at Seven Star Pharma

Single crystal X-ray Diffractometer    

Thermogravimetric analyzer (TGA-5500) instrument at Seven Star Pharma

Thermogravimetric analyzer (TGA)

HPLC instrument at Seven Star Pharma

High Performance Liquid Chromatography (HPLC)

pKa and Log P instrument at Seven Star Pharma

pKa and log P instrument

DVS (IntrinsicPlus) instrument at Seven Star Pharma

DVS Intrinsic (Water Vapor Sorption Analyzer)

Karl Fischer titration (KFT) instrument at Seven Star Pharma

Karl Fischer Titrator (KFT)

Dissolution apparatus at Seven Star Pharma
PLM

PLM

Melting point apparatus (M-565) instrument at Seven Star Pharma

Melting point apparatus

Differential scanning calorimeter (DSC2500) instrument at Seven Star Pharma

Differential scanning calorimeter (DSC)

UPLC instrument at Seven Star Pharma

Ultra Performance Liquid Chromatography (UPLC)

FTIR-Raman (Nicolet iS50 advanced) instrument at Seven Star Pharma

Nicolet iS50 Advanced FTIR-Raman instrument

DVS Adventure instrument at Seven Star Pharma

DVS Adventure (Water Vapor Sorption Analyzer)

Pycnometer at Seven Star Pharma

Pycnometer

Fiberoptic probe for dissolution instrument at Seven Star Pharma

Dissolution apparatus with fiber optic probe

bottom of page