Still a student, Paul Janssen assisted in the development of paracetamol (USP: acetaminophen, often referred to generically under the trademark Tylenol) under the name Perdolan, which would later become well-known.

[3] Paul Janssen founded his own research laboratory in 1953 on the third floor of the building in the Statiestraat, still within the Richter-Eupharma company of his father.

In 1955, he and his team developed their first drug, Neomeritine (ambucetamide), an antispasmodic found to be particularly effective for the relief of menstrual pain.

[4][2] In March 2015, Janssen licensed tipifarnib (a farnesyl transferase inhibitor) to Kura Oncology who will assume sole responsibility for developing and commercialising the anti-cancer drug.

[5] Later in the same month the company announced that Galapagos Pharma had regained the rights to the anti-inflammatory drug candidate GLPG1690 as well as two other compounds including GLPG1205 (a first-in-class inhibitor of GPR84).

[7] In September 2017 it was announced that Janssen teamed up with the Biomedical Advanced Research and Development Authority (BARDA), a unit of the U.S. Department of Health and Human Services, to create pandemic flu vaccines.

[8] On 5 March 2019, the Food and Drug Administration approved Janssen's Spravato (esketamine nasal spray) for treatment-resistant major depressive disorder.

[9] In 2021, Janssen was named as a defendant in a trial against several opioid manufacturers filed by New York Attorney General Letitia Jame.

In June 2010, Centocor Ortho Biotech acquired RespiVert, a privately held drug discovery company focused on developing small-molecule, inhaled therapies for the treatment of pulmonary diseases.

[20] In December 2014, the company announced it would co-develop MacroGenics cancer drug candidate (MGD011) which targets both CD19 and CD3 proteins in treating B-cell malignant tumours.

[27] In 1976, Paul Janssen met Ma Haide (born George Shafik Hatem), a Lebanese-American doctor who had started working in China in 1933.

When Deng Xiaoping opened China to the West in 1978, Janssen sent Paul Appermont and Joos Horsten to set up the project.

[27] In 1983, Janssen signed a cooperation contract to modernize production in an old chemical factory in the city of Hanzhong, in Shaanxi.

[27] Janssen Pharmaceuticals has developed and brought to the market about 70 new active substances (NCE), of which the most well-known are (name may differ): Eight original Janssen drugs have been included on the WHO Model List of Essential Medicines: In 1984, Centocor developed their first product approved by the U.S. Food and Drug Administration (FDA) – a diagnostic test used to detect the rabies virus.

[citation needed] In 1998, the company launched its top-selling monoclonal antibody Remicade (infliximab) for its first FDA approved indication in Crohn's disease.

Centocor also markets ReoPro (abciximab), a biologic agent indicated as an adjunct to coronary angioplasty (PTCA).

In 2009, the U.S. FDA approved Simponi, a human monoclonal antibody for treatment for arthritis, which was co-developed with Medarex, Inc.[37] In 2004, the United States Department of Justice began investigating sales practices surrounding the antipsychotic drug risperidone (Risperdal).

In 2010, the agency joined a whistleblower suit alleging that despite being warned by the U.S. Food and Drug Administration not to promote Risperdal as effective and safe for elderly patients, in whom it was known to be associated with early death, Johnson & Johnson and Janssen Pharmaceuticals paid pharmacists at Omnicare, the largest supplier of pharmaceuticals to nursing homes, tens of millions of dollars in bribes and kickbacks to promote the drug to physicians for this unapproved use.