About Quintara Discovery

Quintara Discovery, a discovery & development specialist based in the San Francisco Bay Area, provides high-quality in vitro ADME profiling, bioanalysis services, and dedicated assay development and compound screening. We have accumulated extensive knowledge and insight in designing high-fidelity assays, obtaining and analyzing critical data, and prioritizing compounds for advancement. The turn-around time for most of these assays are within 2-5 days. We also provide dedicated assay support using RapidFire-MS and traditional plate readers. We stand behind all our assays and results. We provide our customers with best service and value with complimentary insightful consultation on all data we generate. Quintara Discovery strives to be your Partner in Drug Discovery & Development!

Quintara Discovery is located on the 1st floor of 170 Harbor Way at South San Francisco.

Key Services and Capabilities

  • ADME assays: metabolic stability, CYP450 interactions, transporter interactions, solubility, permeability and more.
  • Bioanalysis: non-GLP PK analysis of parent and metabolite compounds (plasma and tissue samples).
  • Assay development: biochemical and cellular assays with multilabel or label-free detections.
  • State-of-the-art equipments and robust & flexible workflow: label-free detection with RapidFire-MS system, API 5000 and 4000, multiple liquid handling stations, and versatile plate-readers.


  • Over 35 years of combined drug discovery and development experiences
  • Successfully progressed over 20 compounds into clinical trials, including an FDA-approved cancer drug (Cometriq™)

Wentao Zhang, Ph.D., Founder

  • Over 13 years of industry experience, most recently as Senior Director of New Lead Discovery at Exelixis, managing key drug discovery platform and functions that include compound collection, lead discovery and optimization, and in vitro ADME.
  • Has evaluated over 200 drug targets for assay development, target validation, lead validation, and lead optimization.
  • Has helped progress over 20 compounds from discovery to clinical development, including candidates in phase 2 and 3 clinical trials and Cometriq™, a kinase inhibitor recently approved for medullary thyroid cancer by the FDA.
  • Has authored and co-authored discovery data package (biology) and preclinical DMPK study reports for IND and NDA filings.
  • Ad hoc member of the NIH study section on assay development and President (2012-13) of Chinese American Bio-pharmaceutical Society (CABS).
  • Obtained his Ph.D. degree in Biophysical Chemistry at University of Wisconsin-Madision, and did post-doctoral research at University of California-Berkeley.

Sean Xiang Wu, Ph.D., Co-Founder

  • Has led a team of scientists for ADME profiling at Exelixis in the last 10 years.
  • Has optimized various ADME assays to improve data quality and reproducibility.
  • Has improved assay throughput with automation in liquid handling and data analysis.
  • Has represented and provided DMPK guidance in over 10 cross-functional project teams, including all ADME support for Cometriq™.
  • Editorial board member of Journal of Biomolecular Screening.
  • Obtained his Ph.D. degree in Biochemistry and Molecular Biology at Georgia Health Sciences University, and did post-doctoral research at Yale University and Novartis Pharmaceuticals.

Julie Ren, Ph.D., Co-Founder

  • Has 12 years of industry experience in drug discovery and development, most recently as Director, Bioanalytical, Nonclinical Development (DMPK) in Exelixis.
  • Has led the discovery bioanalysis and pharmacokinetics, conducting and managing pharmacokinetics, toxicokinetics, PK/PD, PK/efficacy, drug distribution, metabolite identification, cellular uptake evaluations for lead validation and optimization.
  • Has established and managed the GLP bioanalytical laboratory in supporting non-clinical toxicokinetics, clinical pharmacokinectics, metabolism, drug-drug interaction and bioequivalence studies for over twenty IND and one NDA filings. Participated in multiple successful FDA audits.
  • Obtained her Ph.D. in Analytical Chemistry at University of Alabama and did post-doctoral research in Biopharmaceutical Sciences at University of California, San Francisco.


Assay Matrices

Quintara provides a wide variety of metabolic stability assays using the following assay matrices:

  • Liver and intestinal microsomes (human and animal species)
  • Liver and intestinal S9 (human and animal species)
  • Liver cytosol (human and animal species)
  • Hepatocytes (human and animal species)
  • Plasma (human and animal species)
  • Blood (human and animal species)

Assay Results

  • Percent of remaining of parent compounds between +/- cofactor NADPH (microsomes or S9)
  • Percent of remaining of parent compounds between 0 minute and a fixed time (10, 30, or 60 minutes)
  • Intrinsic clearance determined by parent compound disappearance over six time points

CYP450 Inhibition

Enzymes/Substrates (All FDA Preferred)

  • CYP1A2/Phenacetin or Tacrine
  • CYP2B6/Efavirenz
  • CYP2C8/Taxol
  • CYP2C9/Tolbutamide
  • CYP2C19/S-mephenytoin
  • CYP2D6/Bufuralol
  • CYP3A4/Midazolam and Testosterone
  • Other CYP450 isoforms

CYP450 Inhibition Assay Formats

  • IC50 values generated by 7-point dose response curves
  • Percent of inhibition at fixed compound concentration

CYP450 MBI/TDI Assay Formats

  • IC50 shift after preincubation with and without cofactor NADPH using HLM
  • Inactivation kinact and KI determination using HLM or human hepatocytes
  • Irreversible and pseudo-irreversible inhibitor determination by potassium ferricyanide
  • Dialysis and ultrafiltration
  • Supernatant precipitation
  • Partition ratio determination

Detection Formats

  • LC/MS/MS detection with single substrate
  • LC/MS/MS detection with cocktail substrates
  • RapidFire/MS/MS detection with single substrate
  • RapidFire/MS/MS detection with cocktail substrates


Assay Formats

  • P-gp substrate determination by MDR1-MDCK cells (High-throughput)
  • P-gp substrate determination by MDR1-MDCK and MDCK-II cells (FDA recommended method)
  • P-gp inhibitor determination by MDR1-MDCK and MDCK-II cells (FDA recommended method)


Assay and Sample Format

  • We utilize SCIEX API 4000 and API 5000 triple-quadrupole mass spectrometers for robust and sensitive quantitation. We can routinely determine compounds at pg level.
  • Shimadzu Prominence UFLC system provides low carryover, short runtime, and 96-well plate rack changer holding 12 plates for injection in refrigerated condition.
  • We provide qualitative analysis, such as screening for unknown chemicals or metabolites, using various modes of the mass spectrometers.
  • Caliper Sciclone ALH3000 robotic system provides versatile liquid handling and sample preparation capabilities for high data precision, great process speediness, and less human errors.
  • We utilize various sample cleanup strategies such as protein precipitation, liquid-liquid extraction, and solid phase extraction. Very small sample size is needed and the samples may contain multiple analytes and be in various matrices, including plasma, urine, cell culture, tissue samples.


  • In-life PK, TK available through our local partnership, which allows the shortest turnaround time and integrity of the studies.
  • Pharmacokinetics modeling provided using WinNonlin software.

Other Assays

Other Assays Available

  • CYP1A2, CYP2B6, and CYP3A4 induction in hepatocytes (functional assay and mRNA evaluations)
  • Plasma Protein Binding (human and animal species)
  • Reaction Phenotyping (parent disappearing)
  • Kinetic solubility (using DMSO stocks): fast and doesn't need a lot of material
  • Thermodynamic solubility (using solid compounds): gold standard
  • Passive diffusion determination by MDCK cells
  • Permeability by Caco-2 cells: gold standard
  • Label-free detection for biochemical or cell-based samples with RapidFire technology
  • Analytical chemistry: chemical or formulation analysis

Please contact us if you have any other ADME needs. We will be your partner in achieving your drug discovery goals.


Quintara Discovery welcomes inquiries on potential collaboration and partnership opportunities. We offer comprehensive advice on all areas of discovery and preclinical development.

Our ADME profiling platform is available to boost our partner's discovery productivity. For example, the RapidFire-MS system provides a high-throughput platform for high-resolution CYP450 inhibition and TDI assays. A recent poster using our platform and Labcyte Echo platform for TDI was presented at the 2013 SLAS conference in Orlando, FL.(SLAS 2013 TDI Poster)

Our RapidFire-MS platform also enables label-free detection, offering a clear advantage over the traditional systems with artificially labeled probes. This system is ideal for secondary and confirmative assays for any target that produces a small molecule or peptide product. Some good examples include epigenetic and tumor metabolism targets such as IDH1 and HDAC.

Please contact discovery@quintarabio.com for more information.

Contact Us

Contact Information

Shipping Address

Quintara Discovery
170 Harbor Way, Suite 100
South San Francisco, CA 94080


  • We guarantee competitive prices.
  • We provide significant volume discount.
  • Please call in for a quote.

Guaranteed Satisfaction

  • High-quality data with excellent reproducibility
  • Quality control compounds included in every experiment free of charge
  • Fast turn-around time (within 2-5 days)
  • Flexibility in assay design to fit your need