GastroPlus® Timeline

Simulations Plus released its first such pharmaceutical software product, GastroPlus®, in August 1998. GastroPlus is a mechanistically based simulation program that simulates intravenous, oral, oral cavity, ocular, intranasal, and pulmonary absorption, biopharmaceutics, pharmacokinetics, and pharmacodynamics in humans and animals. Since its release, GastroPlus has become the most commonly used software of its kind and has been licensed by most top 25 pharmaceutical companies in the U.S. and Europe, along with international companies in Japan and across Asia. In addition, GastroPlus has been the focus of several recent publications and workshops from the FDA.
  • Bachelor of Aerospace Engineering degree at Auburn University in 1969
  • Master of Administrative Science at the University of Alabama in Huntsville in 1976
Master of Science in aerospace engineering at Auburn University in 1977
He worked in the aerospace industry from 1971-1983 developing simulation and modeling software for the design of solid propellant rocket motors and missile systems.
In 1981, Walt and his wife Virginia ("Ginger") founded Words+, Inc., a California company that offered  the first PC- based communication systems for people with severe disabilities, including starting in  1985, world‐famous theoretical physicist, Professor Sir Stephen Hawking.
In 1983, Walt left the aerospace industry to become the full‐time CEO of Words+ until 1996, when  the passion he had developed in aerospace for computer simulation and modeling drove Walt to apply these technologies in healthcare, developing software tools for pharmaceutical R&D as a way to minimize animal testing, failed clinical trials, delays, and cost.
Walt and Ginger founded Simulations Plus in 1996 and took it public on the Nasdaq stock exchange in 1997 (symbol SLP).




• 8.5 New Features

• Mechanistic Precipitation Model

• Transporter IVIVE

• Default Enzyme Expressions

• Infant Physiologies

• General Features  


Michael Bolger

  • zMichael B. Bolger, Ph.D., Univ. CA San Francisco, Pharmaceutical Chemistry 
  • DOS Programs: 1981 to 1991 – Plot4U, Analab, PKFit, ChromLab (1st commercial), SpecLab, Chemcil, and MolDisp
  • CoCenSys, Inc. (1987 – 1993), Co‐founder – Analogs of Progesterone with allosteric modulatory activity at the GABAA receptor
  • CoCenSys, Inc. (1987 – 1993), Co‐founder – Analogs of Progesterone with allosteric modulatory activity at the GABAA receptor
  • Windows Programs: 1989 to present – MolecuLab, TreeBase, CardioPharm, Cyber Patient, PharmLab, Helixgen, GastroPlus
New Features in 8.6
  • Minipig Physiology 
  • DDI Populations Simulations
  • Customization of PBPK models for disease state simulations

Robert Fraczkiewicz

Robert Fraczkiewicz, M.A. Univ. of Wroclaw, Chemistry, Ph.D. Univ. of  Houston, Chemistry – 

Roztwory, QMPRPlus, QMPRchitect, ADMET Predictor, ANNE log P, ANNE Solubility,  ANNE pKa, ADMET Modeler BFGS Nonlinear Optimizer, HTPK, GPX Optimizer,  GastroPlus Integrator, Classical Nucleation and Growth, pHSol.dll, DDDPlus dynamic  microclimate pH, Solubility vs. pH profiles, Chemically Relevant Principle  Components, Descriptor Sensitivity Analysis, Object‐Oriented Molecular  Descriptors, Atomic Descriptors based on ab initio (B3LYP/6‐311G(d,p)) natural  population analysis (NPA) partial atomic charges, hundreds of molecular  descriptors

New Features in 9.0
  • Expanded AP Module
  • Dermal Model 
  • Oral Cavity Model 
  • Biologics Module 
  • New DDI Standards 
  • Licensing 

John DiBella

John DiBella, M.S., Case Western Reserve, Biomedical  Engineering – 1st DDDPlus (with Walt), Multiple Workshop Case Studies 

New Features in 9.5
  • New ADRM Animal Physiologies
  • New built in PBPK Phsyiologies
  • Population Simulations
  • IVIVC and Virtual BE

Viera Lukacova

Viera Lukacova, Ph.D., North Dakota State Univ.,  Pharmaceutical Sciences, M.S., Slovak Univ. of Technology,  Biochemistry and Biotechnology – 

GastroPlus ver. 5.0 to 9.7, MembranePlus 1.0, Finished Object  Oriented PBPK, Lukacova Single Kp equations, Corrected fup for  plasma lipid, Updated Tissue Fut calculations, Paracellular  Permeability with Zhimin model (Marvin Waldman), Mechanistic  Scaling of Permeability between Species, Drug‐Drug Interactions (DDI), Pediatric subjects, Optimizable Log D Model SA/V 6.1, Virtual  Bioequivalence and Crossover Trials, IVIVC Module (w John Chung),  CVODE integrator, Takano Z‐Factor dissolution method, Supervised  ADRM with Sil Chaudhuri (Pulmonary, Ocular, Dermal), Haiying Zhou  (Oral Cavity) and Jessica Spires, and much more….

New Features in 9.6
  • Faster Simulations 
  • Dynamic intestinal fluid model 
  • Revisited Colon enterocyte Volumes
  • Mechanistic enhancements in ocular model
  • New particle deposition model for pulmonary route
  • Dissolution/precipitation for subcutaneous and intramuscular injections
  • Quick setup of in vitro transdermal permeability assays
  • Revised all human PBPK physiologies
  • Ability to set up more realistic populations and improved handling of covariates in Population Simulation 
  • Additional disease physiologies (obesity, renal impairment)
  • Clearnace mechanisms in blood compartments
  • New enzyme/transporter distribution information 
  • Additional compound model files for substrates & inhibtors 
  • Time scale/shift correlation function 
  • Triple Weibull function 
  • Option to use interpolated in vitro profile for IVIVC
  • Full control over optimization criteria with mechanistic deconvolution 
  • New bacteria killing PD models 
  • Save selected profiles and Excel file outputs in Batch, PSA, and Population Simulator run
  • Create DILIsym input file from GastroPlus Single or Populations simulations 
New Features in 9.7
  • Mechanistic pregnancy PBPK model 
  • Different meal types 
  • Lysosomal trapping for PBPK tissues 
  • Coverage for all major disease/small populations
  • DDI Predictions
  • FIH Dose Selections
  • Formulation Optimization
  • Virtual Population/BE Trial Simulations 
  • Food Effect Modeling 
  • Animal/Human Risk Assessment 
  • Compatible with DILIsym 

Marvin Waldman

Marvin Waldman, Ph.D., Harvard Univ., Chemical Physics – ADMET Predictor, ADMET Modeler, GastroPlus, ab initio (B3LYP/6‐311G(d,p)) Huckel partial atomic charges, Genetic Algorithm Descriptor Sensitivity, Sites of metabolism,  Structural basis for log D vs. pH,  beta Binomial Classification and Regression Model  Errors, Zhimin effective diffusion in microporous membranes, Multi‐threading code in  ADMET Predictor, HTPK, multi‐objective Pareto Molecule Optimization, and much  more …..

David Miller 

David Miller, Ph.D., Univ. CA San Francisco, Biophysics – Classpharmer, ChemTK, MedChem Studio, MedChem Designer, ADMET Predictor  (Refactor), Scaffold based Classes, R‐Table Explorer, Matched Molecular Pairs, Activity  Cliffs, Reaction Transforms, Combinatorial Reactions and Transforms, R‐Table  Explosion (w Walt W.), and much more …..

Bob Clark

Robert D. Clark , Ph.D., Cornell Univ., Biochemistry, Molecular & Cell Biology – 

ADMET Predictor, ADMET Modeler, Delta Models, beta Binomial Classification and  Regression Model Errors, Metabolism and Toxicity Models, S+Peff, ADMET Risk (w/  Walt) w/ soft thresholds, Glucuronidation and Hydrolysis transformations, NCE  Projects, Common ion effect, and much more …..

"Simulations Plus will lead the world in inovative software simulation products. Simulations Plus will work smart to be profitable and maintain dedication to good science. Simulations Plus will achieve high quality in all its products."