- OAK RIDGE NATIONAL LABORATORYUnited States
- ObsEva SASwitzerland
- ObsEva USA, Inc.Switzerland
- Octapharma AGSwitzerland
- October Pharma S.A.E.Egypt
- Ocugen, Inc.United States
- Ocular Therapeutix, Inc.United States
- Oculus SurgicalGermany
- Odimma TherapeuticsFrance
- OleonBelgium
- Olic (thailand) LimitedThailand
- Olimp Laboratories Sp. Z O.o.Poland
- OLON SPAItaly
- OLPHA ASLatvia
- Oman Pharmaceutical ProductsOman
- Omeza, LLCUnited States
- Omni Lens Pvt LtdIndia
- OMSAV PHARMA RESEARCH PRIVATE LTDIndia
- OMYA INCUnited States
- Onco360 Oncology PharmacyUnited States
- OncoBeta GmbHGermany
- Oncoceutics, Inc.United States
- OncoDerm Pharmaceuticals Inc.United States
- OncoDiagnostics Inc.United States
- OncoDynamics Inc.United States
- Oncology Research Group Inc.United States
- Oncolys Biopharma Inc.Japan
- OncoMed Pharmaceuticals, Inc.United States
- OncoPharma Inc.United States
- OncoResearch Inc.United States
- Oncotelic Therapeutics, Inc.United States
- OncoTherapeutics Inc.United States
- OncoTherapies Inc.United States
- OncoTherm GmbHGermany
- OncoTrack Pharmaceuticals Inc.United States
- Oncotype Dx Breast Recurrence Score® TestNetherlands
- OncoVax Pharmaceuticals Inc.United States
- OncovitaFrance
- OncRelief Pharmaceuticals Inc.United States
- Ono Pharmaceutical Co., Ltd.Japan
- Onxeo SAFrance
- Onyx Pharmaceuticals, Inc.United States
- Oogroup - Ophthalmic Pharmaceutical GroupItaly
- Op2lysisFrance
- OpenBiomeUnited States
- Ophthalmic Innovations Inc.United States
- Ophthalmics, Inc.United States
- Opiant Pharmaceuticals, Inc.United States
- OPKO Health, Inc.United States
- OPOCRIN SPAItaly
- Opthea LimitedAustralia
- OPTIMUS DRUGS PRIVATE LTDIndia
- Optimus PharmaIndia
- OptiPharma Inc.United States
- ORANO MED THERANOSTICS SASUnited States
- ORBION PHARMACEUTICALS PRIVATE LTDIndia
- Orbit Genomics Inc.United States
- ORCH LABORATORIES INDIA PVT LTDIndia
- ORCHEV PHARMA PVT LTDIndia
- Orchid Biopharmaceuticals Inc.United States
- Orchid Pharma LimitedIndia
- Orexigen Therapeutics, Inc.United States
- Orexo ABSweden
- Organon & Co.United States
- ORGAPHARM SASFrance
- Oriental AromaticsIndia
- OrifarmDenmark
- Orifarm Healthcare A/SDenmark
- ORIL INDUSTRIEFrance
- Orion CorporationFinland
- Orphan Europe S.a.r.l.France
- Orsini - Rare Disease Pharmacy SolutionsUnited States
- Ortho DermatologicsUnited States
- OSI PharmaceuticalsUnited States
- Osmotica Pharmaceutical Corp.United States
- Oso Biopharmaceuticals Manufacturing, LlcUnited States
- OTSUKA CHEMICAL CO LTDJapan
- OTSUKA CHEMICAL INDIA PRIVATE LTDIndia
- Otsuka Pharmaceutical Co., Ltd.Japan
- Otsuka Pharmaceutical Development & Commercialization, Inc.United States
- Owen MumfordUnited Kingdom
- Oxford Biomedica plcUnited Kingdom
- OXTherapeutics Inc.United States
- Oyster Point PharmaUnited States