Services

Log P is a measure of lipophilicity, or the ratio of compound that partitions between octanol and water.  As the value increases, so does the lipophilicity of the compound.  The determination is based on potentiometric titration, with results comparable to the shakeflask technique.  Results are reported using the lipophilicity profile, a plot of log D versus pH. We routinely measure log P between -2 and 5.

Potentiometric titration is especially useful for zwitterions and problems associated with ion-pair formation, and micro-emulsion in the shake-flask method.  pION has the capability to perform experiments with other partitioning media such as cyclohexane, heptane, and liposomes.

To submit your compounds for analysis:

• Fill out a Sample Submission Form for EACH compound.  Also, fill out the Sample Input Template (enter all samples), and send a printout with the samples to pION
• Please include the Purchase Order number on the sample submission forms

pION Biopharma Services methods are API-sparing which typically requires a few milligrams or less, so you can screen samples earlier, thus saving resources for only the best candidates.  Analysis is performed by our experienced and knowledgeable chemists with instrumentation conditions tailored specifically for each experiment. 

Permeability

     GIT PAMPA Submission Form

     BBB PAMPA Submission Form 

Solubility

     Miniaturized Shake Flask UV Submission Form

     Miniaturized Shake Flask HPLC (contact pION)

Solubility and/or Dissolution

     µDISS Profiler™ (contact pION)

Ionization and Lipophilicity

     pKa/log P/log D Submission Form

BCScan and BCScreen

     (contact pION)

To submit samples

• Fill out the sample submittal forms, one for each sample. 
• Include a purchase order number for payment.
• Ship the completed form with your samples to pION.
• Missing information will delay sample turnaround.

API Sparing Dissolution  Small volume dissolution measurements magnify differences amongst polymorphic or salt compounds. Monitoring concentration over time can determine stability and excipient effects on drug compounds. A concentration-time profile provides important information about the API’s physical properties including dissolution rate, precipitation, polymorphic changes, salt selection and stability. Only milligram amounts of API is required for this method.

Permeability is often one of the toughest development hurdles for a drug candidate. With variable pH, active and passive absorption as well as lipo- and hydrophilicity to consider, screening large numbers of compounds with cell based assays is difficult and expensive.

The Parallel Artificial Membrane Permeability Assay (PAMPA) utilizes a synthetic model for permeability. Its ease of operation, flexibility, and reproducibility can accelerate throughput for passive permeability measurements. PAMPA is a high-throughput and cost-effective assay that provides early feedback during screening and development, while Caco-2 can be used later for mechanistic permeability studies to reveal active transport and efflux.

pION also conducts Caco-2 permeability assays.  The P-glycoprotein (P-gp) inhibitor, verapamil, can be included to identify whether active transport is mediated by P-gp.  Our experience in permeability allows us to measure Caco-2 in low solubility/high permeability compounds when other labs may fail.


Blood-Brain Barrier  The PAMPA assay is also a highly cost-effective method for CNS screening of candidate drug molecules. Using a mixture of phospholipids infused into lipophilic microfilters, with net negative lipid charge, the BBB PAMPA system mimics many of the properties of brain lipid membranes. The assay is highly correlated with rodent in vivo and in situ studies of the kinetics of drug uptake across the BBB.  While in vivo kinetic studies are time consuming and expensive, in contrast, BBB PAMPA can be employed early in screeeing and drug development in a very cost-effective manner. During later stages, animal studies can be augmented by BBB PAMPA as well.

Physicochemical Profiles

Permeability – pION’s Double-Sink™ PAMPA assay is commonly performed at 3 pH values: 5.0, 6.5 and 7.4, but can be conducted anywhere between 3-10. The compound’s permeability is compared to standard compounds, and can be used to predict human intestinal permeability.  Well-characterized BCS classified compounds can be included in the sample runs to provide classification boundary limits between high and low permeability classes.

Solubility - Equilibrium solubility measurements are performed using pION’s patented miniaturized shake flask method. Measurements are done either at one pH, or user defined pH values.

pK_a – pION has the instrumentation and expertise to determine the pK_a values of compounds with extremely low-aqueous solubility, high molecular weight, and multiple, overlapping ionization constants. pK_a measurements are performed by either spectrophotometric or potentiometric methods. Drug ionization profiles explain the behavior of drug molecules. As a drug molecule ionizes into species with different charges, its physical, chemical and biological properties are also affected. 

log P - The octanol-water partition coefficient (lipophilicity as a function of pH) is used in combination with the pK_a to predict the distribution of a drug compound in a biological system. Factors such as absorption, excretion and penetration of the CNS may be related to the log P of a drug.

 Biopharmaceutics Classification System (BCS) Profiles  BCS is described in an FDA guidance for classifying drugs based on solubility and permeability properties. The BCS classification system can be applied to NDA and ANDA approvals as well as to scale-up and post approval changes in drug manufacturing. Biopharmaceutical companies can forego clinical bioequivalence studies if their product meets the specification detailed in the guidance. pION’s expertise in measuring drug permeability, solubility and dissolution can help companies conform to FDA guidelines for BCS classification. This can save a significant amount of development time and reduce associated costs. pION provides BCScreen, a limited set of physicochemical measurements, or the BCSubmit service, which features a comprehensive set tests that include ionization, lipophilicity, dissolution, solubility, permeability by Double-Sink PAMPA™ and Caco-2.

in vitro Pharmaco-Kinetic (PK) Profiles  pION has developed an in vitro assay similar to PK studies that ranks excipients based on their effect on flux by measuring the combined net effect of permeability and solubility of compounds. This new approach for excipient screening has the following advantages:

• Fast turnaround
• Easy to conduct 
• Accomodates low solubility compounds
• Excipient UV absorbance does not interfere
• Less expensive than individual permeability and solubility measurements

Forced Degradation Studies.  Using an HPLC stability indicating assay, the effect of temperature, pH, and hydrolysis (acid or base) on drug compounds is determined for user specified time periods.