| Company Name [asc] | Country |
|---|---|
| OncoNano Medicine Limited | Ireland |
| Onconova Europe GmbH | Germany |
| Oncopeptides AB (publ) | Sweden |
| Oncoradiomics S.A. | Belgium |
| Oncoral Pharma ApS | Denmark |
| Oncorena AB | Sweden |
| Oncoscience GmbH | Germany |
| Oncostellae S.L. | Spain |
| OncoZenge AB | Sweden |
| One-carbon Therapeutics AB | Sweden |
| OneChain Immunotherapeutics, S.L. | Spain |
| Oniria Therapeutics S.L. | Spain |
| Onkogen Kft. | Hungary |
| onkovis GmbH | Germany |
| Onni Biotechnologies Oy | Finland |
| OP Pharma SRL | Italy |
| Op2Lysis | France |
| OPERON, S.A. | Spain |
| Optimal Regulatory Solutions, S.L.U. | Spain |
| Opus Materia Ltd | Greece |
| Oranda Therapeutics Limited | Ireland |
| Oresund Pharma ApS | Denmark |
| Orexa B.V. | Netherlands |
| ORKEO | France |
| ORNYX OÜ | Estonia |
| Orphalan | France |
| ORPHELIA Pharma | France |
| Orphelion AB | Sweden |
| Orphix Consulting GmbH | Germany |
| ORYX GmbH & Co. KG | Germany |
| Oryzon Genomics, S.A. | Spain |
| Osalia | France |
| OSE Immunotherapeutics | France |
| OSIVAX | France |
| OT4B | France |
| OvoVet Pharma SRL | Romania |
| Ovum SPF S.L. | Spain |
| Oxcia AB | Sweden |
| Oxolife SL | Spain |
| Ozack ApS | Denmark |
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