Pion measures lipophilicity with octanol/water and other partitioning media such as cyclohexane, heptane, and liposomes.

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 ion-pairing; formation of micro-emulsions is easily overcome with this method.  

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. 

Ionization Lipophilicity, Permeability, Solubility, BCScan and BCScreen

Universal Submission Form

Real-Time Solubility and/or Dissolution

     µDISS Profiler™ (contact Pion)

To submit samples

• This form contains guidance for sample quantities required.
• Fill out a sample submittal form, 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.

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 screening 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 
• Accommodates 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.  

Determination and prediction of solubility, dissolution, permeability and human absorption is Pion’s core business. We screen and analyze pharmaceutical compounds using instrumentation, software and laboratory services.

Meeting the Challenge. Typically, a large pharmaceutical company will test over 3,000,000 molecules for activity. While about 30,000 "hits" may be discovered in a year, only about 30 candidate molecules reach the development stage. Finally only 3 molecules enter the market as drugs, and rarely are these "blockbusters". More often than not, only one molecule reaches consumers.

Drugability - Getting The Job Done. Active compounds often are rejected due to poor oral absorption pharmacokinetics: while they may perform well in a test tube, in the body they just can’t reach their target sites. For example, the molecule may be just too insoluble in water, and like "brick dust" it is eliminated before it has a chance to interact. In order to reach a site of therapeutic action, a molecule has to traverse many barriers. These barriers are formed by cell membranes, composed of oily phospholipid bilayers, which block the passage of charged or hydrophilic molecules. If a molecule is highly charged, it will be highly soluble but then it will not pass these oily barriers. Other effects, such as metabolism and efflux will also limit absorption.

The Need for Better Prediction. Many candidate molecules fail because they cannot cross the phospholipid bilayer to reach their intended target. Laboratory test animals usually are not used during early screening for absorption efficiency. Although epithelial cell cultures such as Caco-2 are often used for this purpose, the tests are costly and require a licensing fee. There are much more effective approaches appropriate for early screening; absorption properties can be assessed by measuring the model-membrane bilayer permeability coefficient, the aqueous solubility and extent of retention by the membrane. This is often referred to as the acronym PSR (permeability-solubility-retention).

For ionizable molecules, the PSR parameters are dependent upon pH. At a given pH, the PSR parameters indicate the charge state of a drug molecule and its solubility in water and membranes, which predict in vivo absorption into the circulatory system. PSR profiles are used to prioritize molecules for further study and to reject some molecules altogether.

Solutions. Pion offers a range of instruments and analytical services that improve lead generation, optimization and selection. All our solutions include API-sparing techniques designed to measure and predict the critical physicochemical properties of target molecules.

At Pion, we specialize in the measurement of absorption related physicochemical parameters such as permeability, solubility, dissolution, and ionization.  Our instruments allow Biopharmaceutical companies to conduct early phase screening of their drug compounds using API-sparing methods that will identify and focus scarce research resources on the most promising candidates.