sean (Xun) gUO PHD
Founder and Principal Consultant
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PA Pharma CMC Consulting, LLC (PPCC) is a Boston, Massachusetts-based privately held limited liability corporation dedicated to supporting pharmaceutical and biotechnology companies with expertise in analytical development, quality control, and CMC regulatory services. Our mission is to help clients achieve successful development and approval of their drug products, and it is our responsibility to do so in a GxP-compliant manner. The company was founded by Dr. Sean Guo, a seasoned analytical and QC expert with a proven track record in pharmaceutical CMC for both small molecules and oligonucleotide-based drug substances and drug products in GxP-regulated environments. When client needs extend beyond our core expertise, we are happy to offer trusted technical referrals to ensure comprehensive support.
About Dr. SEAN GUO
About Dr. SEAN GUO
Over the course of my 14-year career as a CMC analytical development scientist in the pharmaceutical and biopharmaceutical industry, I have acquired extensive and valuable experience across a broad range of areas. These include analytical method development, qualification and validation, QC release and stability testing, OOS/OOT investigations and root cause analysis, preparation of CTD Module 3 for IND/IMPD/CTA submissions, responses to questions (RTQs), SOP authorship, and both intramural and extramural collaboration. I have also overseen analytical QC activities of contract partners and contributed to cross-functional project execution.
My expertise spans both drug substances and drug products across various dosage forms, including immediate-release, gastro-retentive, and extended-release tablets, drug-in-capsule (DiC) formulations, as well as parenteral and injectable products. I possess a strong analytical technical background and serve as a subject matter expert in qNMR, 1D/2D NMR structure characterization, UHPLC, LC-MS, GC-FID, GC-MS, and dissolution/disintegration testing in GMP-regulated environments. Click buttons below for my full resume or one page summary.
key career highlights:
key career highlights:
Proven Track Records and Key Expertise:
In Biogen Inc, lead all analytical development and quality control GLP/GMP activities for five small-molecule programs and one oligonucleotide program, covering both DS and DP from FIH through Phase 3 clinical trials. This included in-house wet-lab work and CDMO supervision.
Successfully collaborated with over 10 CDMOs in USA, Canada, UK, Italy, Switzerland, Japan, China and India.
Contributed to successful submission of over 10 IND, IMPD and CTA filings to regulatory agencies, including the FDA, EMA, IMP, and PMDA, by authoring the analytical, quality control, and stability sections of CTD Module 3. Additionally, performed cross-functional reviews of all other Module 3 sections.
Successfully completed all RTQs from regulatory agencies, meeting the targeted timeline for clinical trials.
Successfully completed all OOS/OOT troubleshooting and root-cause investigations for DS and DP method development/validation and QC release testing issues, in full compliance with ICH guidelines and with a focus on ensuring patient safety. Some of these efforts led to the publication of three publications in peer-reviewed pharmaceutical industry journals.
In Johnson Matthey Pharmaceutical Services, lead all analytical method development, qualification/validation activities, QC release testing as well as client communications for four late-stage and commercial small-molecule DS programs.
Combined, developed and validated over 100 U/HPLC, GC, LC-MS, and qNMR methods for GMP release of related substances, DS and DP. Lead structure characterization of more than100 reference standards and reference markers using 1D/2D NMRs, LC-MS, FT-IR, UV/Vis and Elemental Analysis technologies.
Recent Publications in Pharmaceutical Industry Journals:
20. Guo, X.,* Miller, W., Zangi, M., McElderry, J.D. “Application of Quantitative NMR in Pharmaceutical Analysis: Method Qualification and Potency Determination for Two New Chemical Entities in Early-Stage Clinical Studies” J. Pharm. Biomed. Anal. 2023, 234, 115561.
Developed two qNMR test methods to determine %wt/wt potency for two new chemical entities for early-stage clinical studies
qNMR potency results were determined to be comparable to conventional LC-based potency results
A new sample preparation procedure is reported that prevents potential analyte/internal standard mutual contamination
The qNMR approach is a more sustainable and economical approach to potency determination
19. Guo, X.,* Zou, L.,* McElderry, J.D., Li, J. “Platform HS-GC-FID Method for High-Throughput Determination of Residual Solvents in Pharmaceutical Materials.” J. Pharm. Biomed. Anal, 2023, 229, 115349.
A headspace GC method was developed to quantify 27 residual solvents.
The method was validated thoroughly using two representative sample matrices.
The method was robust against slight variation of several critical parameters.
The method is sustainable, economical, user-friendly and error-proofing.
18. Guo, X.,* Stolee, J.A.,* Fillon, Y.A, Zou, L. “Trace-Level Determination of Acrylonitrile Generated in the Manufacturing Process of Oligonucleotides by Static Headspace Gas Chromatography with an Electron Impact(+) Mass Detector.” OPR&D, 2021, 25, 318-326
Developed and qualified a platform method for determining trace amount of acrylonitrile (class 2b genotoxic impurity per ICH M7) in oligonucleotide DS and process intermediates by HS-GCMS
Method robustness tested and demonstrated with various reaction matrix used in the solid phase synthesis of oligonucleotide DS
Determined degradation kinetics of acrylonitrile in backbone deprotection and ammonolysis matrix respectively
Acrylonitrile was demonstrated to degrade quantitatively and rapidly in the ammonolysis sample matrix
Academic Publications:
17. Guo, X., Crnovcic, I., Chang, C., Luo, J., Lohman, J., Papinski, M., Bechthold, A., Horsman, G., Shen, B.* “PokMT1 from the polyketomycin biosynthetic machinery of Streptomyces diastatochromogenes Tü6028 belongs to the emerging family of C-methyltransferases that act on CoA-activated aromatic substrates.” Biochemistry, 2018, 57 (6): 1003-1011
16, Guo, X., Crawford, J.* “An Atypical Orphan Carbohydrate-NRPS Genomic Island Encodes a Novel Lytic Transglycosylase.” Chemistry & Biology, 2014, 21, 1271-1277.
15. Ge, H.M., Huang, T.T., Rudolf, J.D., Lohman, J.R., Huang, S.X., Guo, X., Shen, B.* “The Ketoreductase Domains of Enediyne Polyketide Synthases Stereospecifically Reduce the b-Ketoacyl Intermediates to b-D-Hydroxyacyl Intermediates in Enediyne Core Biosynthesis.” Org. Lett, 2014, 16, 3958-3961.
14. Vizcaino, M.I., Guo, X., Crawford, J.M.* “Merging Chemical ecology with bacterial genome mining for secondary metabolite discovery.” J. Ind. Microbiol. Biotechnol. 2014, 41, 285-299.
13. Lin, S.J., Huang, T.T., Horsman, G.P., Huang, S.X., Guo, X., Shen, B.* “Specificity of the Ester Bond Forming Condensation Enzyme SgcC5 in C-1027 Biosynthesis.” Org. Lett. 2012, 14, 2300-2303.
12. Guo, X., Liu, T.G., Deng, Z.X., Cane, D.E.* “Essential Role of the Donor Acyl Carrier Protein in Stereoselective Chain Translocation to a Fully Reducing Module of the Nanchangmycin Polyketide Synthase.” Biochemistry 2012, 51, 879-887.
11. Guo, X., Liu, T.G., Valenzano, C.R., Deng, Z.X., Cane, D.E.* “Mechanism and Stereospecificity of a Fully Saturating Polyketide Synthase Module: Nanchangmycin Synthase Module 2 and Its Dehydratase Domain.” J. Am. Chem. Soc. 2010, 132, 14694-14696.
10. Sheng X., Guo X., Lu X.M., et. al. ” DNA Binding, Cleavage, and Cytotoxic Activity of the Preorganized Dinuclear Zinc(II) Complex of Triazacyclononane Derivatives.” Bioconjugate Chemistry 2008, 19, 490-498.
9. Guo X., Zhang L., Lu G.Y.,* et. al. ”Interfacial behaviors of azocalixarene derivatives at the air/water interface and photochromism in the Langmuir-Blodgett films.” Chinese Chem. Lett. 2005, 16, 1543-1546.
8. Guo X., Liu F., Lu G.Y.* “Recent progress on study of calixarene derivatives.” Chinese J. Org. Chem. 2005, 25, 1021-1028.
7. Guo X., Zhang L., Lu G.Y.,* et al. “p-nitrophenylazo calix[4]arenes, synthesis, monolayers and NLO-properties.” Supramolecular Chem. 2005, 17, 271-276.
6. Guo X., Lu G.Y.,* Li Y. “Interaction between calix[4]arene derivative bearing adenino units and complementary nucleosides at the air-water interface.” Thin Solid Films 2004, 460, 264-268.
5. Bai Z, Yu L, Lu G.Y.,* Guo X. “Synthesis of (p-formylphenyl)azo calyx[4]arenes” Chinese J. Chem. 2004, 22, 498-501.
4. Wang Z.S., Lu G.Y.,* Guo X., et al. “Synthesis of calix[4]arene derivatives containing a nucleobase and their interaction with complementary nucleosides at the air-water interface.” Supramolecular Chem. 2003, 15, 327-334.
3. Wang Z.S., Lu G.Y.,* Sheng X., Guo X., et al. ”Interaction and interfacial molecular recognition of calix[4]arene derivatives bearing nucleobases for complementary nucleoside.” Chinese J. Chem. 2003, 21, 600-603.
2. Jin C.M., Gui M.Z., Lu G.Y.,* Guo X., et al. “Studies on properties of p-nitrophenylazo calix[4]arene derivatives.” Chinese J. Chem. 2003, 21, 105-107.
1. Wan X.B., Jin C.M., Guo X., Lu G.Y.* “Synthesis of Schiff base calix[4]arene crowns.” Chinese Chem. Lett. 2002, 13, 699-700.
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