Bayer

World War I

During World War I (1914–1918), Bayer's assets, including the rights to its name and trademarks, were confiscated in the United States, Canada and several other countries. In the United States and Canada, Bayer's assets and trademarks, including the well-known Bayer cross, were acquired by Sterling Drug, a predecessor of Sterling Winthrop and were not reclaimed until 1994.

Throughout the war, Bayer was involved in production and development of various chemical weapons. In 1914, Bayer manufactured dianisidine chlorosulfate for use in 105 mm artillery shell, intended as a lung irritant against British forces.

In 1916, Bayer scientists discovered suramin, an anti-parasite drug that is still sold by Bayer under the brand name Germanin. The formula of suramin was kept secret by Bayer for commercial reasons, but it was elucidated and published in 1924 by Ernest Fourneau and his team at the Pasteur Institute. It is on the World Health Organization's List of Essential Medicines.

IG Farben

In 1925, Bayer became part of IG Farben, a German conglomerate formed from the merger of six chemical companies: BASF, Bayer, Hoechst (including Cassella and Kalle & Co.), Agfa, Chemische Fabrik Griesheim-Elektron, and Chemische Fabrik vorm. Weiler Ter Meer. In the 1930s, Gerhard Domagk, director of Bayer's Institute of Pathology and Bacteriology, working with chemists Fritz Mietzsch and Joseph Klarer, discovered prontosil, the first commercially available antibacterial drug. The discovery and development of this first sulfonamide drug opened a new era in medicine. Domagk won the Nobel Prize in Physiology or Medicine in 1939 "for the discovery of the antibacterial effects of prontosil". He was forced by the Nazi Party to relinquish the reward; German citizens had been forbidden from accepting Nobel prizes since the Nobel committee had awarded the 1935 Nobel Peace Prize to a German pacifist, Carl von Ossietzky.

World War II and the Holocaust

IG Farben, Bayer's parent company, used slave labour in factories it built in Nazi concentration camps, most notably in the Monowitz concentration camp (known as Auschwitz III), part of the Auschwitz camp complex in German-occupied Poland. By 1943, almost half of IG Farben's 330,000-strong workforce consisted of slave labour or conscripts, including 30,000 Auschwitz prisoners.

Helmuth Vetter, an Auschwitz camp physician, SS captain and employee of the Bayer group within IG Farben conducted medical experiments on inmates at Auschwitz and at the Mauthausen concentration camp. In one study of an anaesthetic, the company paid RM 170 per person for the use of 150 female inmates of Auschwitz. A Bayer employee wrote to Rudolf Höss, the Auschwitz commandant: "The transport of 150 women arrived in good condition. However, we were unable to obtain conclusive results because they died during the experiments. We would kindly request that you send us another group of women to the same number and at the same price."

After the war, the Allied Control Council seized IG Farben for "knowingly and prominently... building up and maintaining German war potential". It was split into its six constituent companies in 1951, then split again into three: BASF, Bayer and Hoechst. Bayer was at that point known as Farbenfabriken Bayer AG; it changed its name to Bayer AG in 1972. After the war, some employees of Bayer appeared in the IG Farben Trial, one of the Nuremberg Subsequent Tribunals under US jurisdiction. Among them was Fritz ter Meer, who helped to plan the Monowitz camp (Auschwitz III) and IG Farben's Buna Werke factory at Auschwitz, where medical experimentation had been conducted and where 25,000 forced laborers were deployed. Ter Meer was sentenced to seven years, but was released in 1950. Despite being a convicted Nazi war criminal, Ter Meer was elected as chairman of Bayer AG's supervisory board in 1956, a position he retained until 1964.

Helge Wehmeier, then CEO of Bayer, offered a public apology in 1995 to Elie Wiesel for the company's actions during World War II (1939–1945) and the Holocaust.

Bayer has been involved in other controversies regarding its drug products. In the late 1990s it introduced a statin drug, Baycol (cerivastatin), but after 52 deaths were attributed to it, Bayer discontinued it in 2001. The side effect was rhabdomyolysis, causing kidney failure, which occurred with a tenfold greater frequency in patients treated with Baycol in comparison to those prescribed alternate medications of the statin class. Trasylol (aprotinin), used to control bleeding during major surgery, was withdrawn from the market worldwide in 2007 when reports of increased mortality emerged; it was later re-introduced in Europe but not in the US.

Top-selling pharmaceutical products

In 2014, pharmaceutical products contributed €12.05 billion of Bayer's €40.15 billion in gross revenue. In 2019, identified "key growth" products were Xarelto (rivaroxaban), Eylea (aflibercept), Stivarga (regorafenib), Xofigo (radium-223), and Adempas (riociguat). Top-selling products as of 2014 included:

Kogenate (recombinant clotting factor VIII). Kogenate is a recombinant version of clotting factor VIII, the absence or deficiency of which causes the abnormal bleeding associated with haemophilia type A. Kogenate is one of several commercially available Factor VIII products having equivalent efficacy.

Xarelto (rivaroxaban) is a small molecule inhibitor of Factor Xa, a key enzyme involved in blood coagulation. In the United States, the FDA has approved rivaroxaban for the prevention of stroke in people with atrial fibrillation, for the treatment of deep vein thrombosis and pulmonary embolism, and for the prevention of deep vein thrombosis in people undergoing hip surgery. Rivaroxaban competes with other newer generation anticoagulants such as edoxaban, apixaban, and dabigatran as well as with the generic anticoagulant warfarin. It has similar efficacy to warfarin and is associated with a lower risk of intracranial bleeding, but unlike warfarin there is no established protocol for rapidly reversing its effects in the event of uncontrolled bleeding or the need for emergency surgery.

Betaseron (interferon beta-1b) is an injectable form of the protein interferon beta used to prevent relapses in the relapsing remitting form of multiple sclerosis. Betaseron competes with other injectable forms of interferon beta, glatiramer acetate, and a variety of newer multiple sclerosis drugs, some of which can be taken orally (Dimethyl fumarate, teriflunomide, others).

Yasmin / Yaz birth control pills are part of a group of birth control pill products based on the progestin drospirenone. Yaz is approved in the United States for the prevention of pregnancy, to treat symptoms of premenstrual dysphoric disorder in women who choose an oral contraceptive for contraception, and to treat moderate acne in women at least 14 years of age who choose an oral contraceptive for contraception. The FDA conducted a safety review regarding the potential of Yaz and other drospirenone-containing products to increase the risk of blood clots; Yaz and Yasmin were associated with the deaths of 23 women in Canada, leading Health Canada to issue a warning in 2011. Although conflicting results were obtained in different studies, the FDA added a warning to the label in 2012 that Yaz and related products may be associated with an increased risk of clotting relative to other birth control pill products. Subsequently, a meta analysis suggested that birth control pills of the class Yasmin belongs to raise the risk of blood clots to a greater extent than some other classes of birth control pills.

Nexavar (sorafenib) is a kinase inhibitor used in the treatment of liver cancer (hepatocellular carcinoma), kidney cancer (renal cell carcinoma), and certain types of thyroid cancer.

Trasylol (Aprotinin) Trasylol is a trypsin inhibitor used to control bleeding during major surgery. In a 2006 meeting called by the FDA to review the drug's safety, Bayer scientists failed to reveal the results of an ongoing large study suggesting that Trasylol may increase the risks of death and stroke. According to a FDA official who preferred to remain anonymous, the FDA learned of the study only through information provided to the FDA by a whistleblowing scientist who was involved in it. The study concluded Trasylol carried greater risks of death, serious kidney damage, congestive heart failure and strokes. On 15 December of the same year, the FDA restricted the use of Trasylol, and in November 2007, they requested that the company suspend marketing. In 2011, Health Canada lifted its suspension of Trasylol for its originally approved indication of limiting bleeding in coronary bypass surgery, citing flaws in the design of the studies that led to its suspension. This decision was controversial. In 2013, the European Medicines Agency lifted its suspension of the Trasylol marketing authorization for selected patients undergoing cardiac bypass surgery, citing a favorable risk-benefit ratio.

Cipro (ciprofloxacin) Ciprofloxacin was approved by the US Food and Drug Administration (FDA) in 1987. Ciprofloxacin is the most widely used of the second-generation quinolone antibiotics that came into clinical use in the late 1980s and early 1990s. In 2010, over 20 million outpatient prescriptions were written for ciprofloxacin, making it the 35th-most commonly prescribed drug, and the 5th-most commonly prescribed antibacterial, in the US.

Rennie antacid tablets, one of the biggest selling branded over-the-counter medications sold in Great Britain, with sales of £29.8 million.

Agricultural

Bayer produces various fungicides, herbicides, insecticides, and some crop varieties.

Fungicides are primarily marketed for cereal crops, fresh produce, fungal with bacteria-based pesticides, and control of mildew and rust diseases. Nativo products are a mixture of trifloxystrobin tebuconazole. XPro products are a mix of bixafen and prothioconazole, while Luna contains fluopyram and pyrimethanil.

Herbicides are marketed primarily for field crops and orchards. Liberty brands containing glufosinate (a.k.a. Liberty or Basta) are used for general weed control. Capreno containing a mixture of thiencarbazone-methyl and tembotrione is used for grass and broad-leaf control.

Insecticides are marketed according to specific crop and insect pest type. Foliar insecticides include Belt containing flubendiamide, which is marketed against Lepidopteran pests, and Movento containing spirotetramat, which is marketed against sucking insects. Neonicotinoids such as clothianidin and imidacloprid are used as systemic seed treatments products such as Poncho and Gaucho. In 2008, neonicotinoids came under increasing scrutiny over their environmental impacts starting in Germany. Neonicotinoid use has been linked in a range of studies to adverse ecological effects, including honey-bee colony collapse disorder (CCD) and loss of birds due to a reduction in insect populations. In 2013, the European Union and a few non EU countries restricted the use of certain neonicotinoids. Parathion was discovered by scientists at IG Farben in the 1940s as a cholinesterase inhibitor insecticide. Propoxur is a carbamate insecticide that was introduced by Bayer in 1959.

Other acquisitions

In November 2010, Bayer AG signed an agreement to buy Auckland-based animal health company Bomac Group. Bayer partnered on the development of the radiotherapeutic Xofigo with Algeta, and in 2014, moved to acquire the company for about $2.9 billion. In 2014, Bayer agreed to buy Merck's consumer health business for $14.2 billion which would provide Bayer control with brands such as Claritin, Coppertone and Dr. Scholl's. Bayer would attain second place globally in nonprescription drugs. In June 2015, Bayer agreed to sell its diabetic care business to Panasonic Healthcare Holdings for a fee of $1.02 billion.

In August 2019, the business acquired the ≈60% of BlueRock Therapeutics it didn't already own for up to $600 million.

In August 2020, Bayer announced it had acquired KaNDy Therapeutics Ltd, helping to boost its female healthcare business, for $425 million. In October, Bayer agreed to acquire Asklepios BioPharmaceuticals for $2 billion upfront.

In June 2021, the company announced it acquired Noria Therapeutics Inc. and PSMA Therapeutics Inc. gaining rights to a number of cancer-based investigational compounds based on actinium-225.

In May 2026, Bayer announced its plans to buy Perfuse Therapeutics, a biopharmaceutical company, for up to $2.45 billion—including a $300 million upfront payment.

Bayer owns the Bundesliga football club Bayer Leverkusen.

Spin off of Covestro

In September 2015, Bayer spun out its $12.3 billion materials science division into a separate, publicly traded company called Covestro in which it retained about a 70% interest. Bayer spun out the division because it had relatively low profit margins compared to its life science divisions (10.2%, compared with 24.9% for the agriculture business and 27.5% for healthcare) and because the business required high levels of investment to maintain its growth, and to more clearly focus its efforts and identity in the life sciences. Covestro shares were first offered on the Frankfurt Stock Exchange in October 2015. Effective January 2016 following the spinout of Covestro, Bayer rebranded itself as a life sciences company, and restructured into three divisions and one business unit: Pharmaceuticals, Consumer Health, Crop Science, and Animal Health.

Acquisition of Monsanto

In May 2016, Bayer offered to buy U.S. biotechnology company Monsanto for $62 billion. Shortly after Bayer's offer, Monsanto rejected the acquisition bid, seeking a higher price. In September 2016, Monsanto agreed to a $66 billion offer by Bayer. In order to receive regulatory approval, Bayer agreed to divest a significant amount of its current agricultural assets to BASF in a series of deals. On 21 March 2018 the deal was approved by the European Union, and it was approved in the United States on 20 May 2018. The sale closed on 7 June 2018. The Monsanto brand was discontinued; its products are now marketed under the Bayer name. On 16 September 2019, under the approval of National Company Law Tribunal, Bayer completed the merger of Monsanto India.

Bayer's Monsanto acquisition is the biggest acquisition by a German company to date. However, owing to ongoing litigation concerning the Monsanto's herbicide Roundup and the massive financial and reputational setbacks it has caused Bayer, the deal is considered one of the worst corporate mergers in history. By 2023, Bayer's market value had declined by over 60% since its 2016 merger, leaving the company's overall worth at less than half of what it paid to acquire Monsanto.

One A Day Vitamins

In 2019, a federal jury in San Francisco sided with Bayer in a $600 million (US) class action suit alleging that the company misinformed consumers by promoting its One A Day vitamins as supporting cardiac health, vigorous immune systems and boosting user energy. The suit was first filed as a nationwide class action; in 2017, the US District Court in San Francisco said subclasses of purchasers of the vitamin in Florida, New York and California could act together.

The jury found that the plaintiffs failed to prove that Bayer misrepresented its One A Day claims, and also did not demonstrate that any of the class representative consumers who purchased One A Day relied on the so-called false information as part of their buying decision.

HIV contamination

In the mid-1980s, when Bayer's Cutter Laboratories realized that its blood products, the clotting agents Factor VIII and IX, were contaminated with HIV, the financial investment in the product was considered too high to destroy the inventory. Bayer misrepresented the results of its own research and knowingly supplied hemophilia medication tainted with HIV to patients in Asia and Latin America, without the precaution of heat treating the product, recommended for eliminating the risk. As a consequence, thousands who infused the product tested positive for HIV and later developed AIDS.

Dicamba

On 14 February 2020, Bayer and BASF were ordered to pay Missouri peach farmer Bill Bader $15 million in damages as a result of destruction of his peach trees which was caused by the usage of dicamba by nearby farmers. Dicamba was another product which Bayer acquired from Monsanto. Bayer also inherited the lawsuit from Monsanto as well. On 15 February 2020, Bayer—representing Monsanto—and BASF were ordered to pay not only the $15 million in damages, but an additional $250 million in punitive damages. Bayer and BASF afterwards announced plans to appeal the $265 million fine.

In June 2020, Bayer agreed to a settlement of up to $400 million for all 2015 to 2020 crop year dicamba claims, not including the $265 million judgement. On 25 November 2020, U.S. District Judge Stephen Limbaugh Jr. reduced the punitive damage amount in the Bader Farms case to $60 million.

PCB pollution

In June 2020, Bayer agreed to pay $800 million to settle lawsuits in a variety of jurisdictions which claimed contamination of public waterways with PCBs by Monsanto before 1978. On 25 November 2020, however, U.S. District Judge Fernando M. Olguin rejected Bayer's settlement offer, which was now at $650 million, and allowed Monsanto-related lawsuits involving PCB to proceed.

Talc-related liabilities

On 4 April 2023, a Delaware judge dismissed a lawsuit by Merck & Co's seeking to hold Bayer responsible for more talc-related liabilities, stemming from its $14.2 billion purchase of Merck's consumer care business in 2014. The judge called Bayer's interpretation of the purchase agreement "the only reasonable one", and said letting Merck "dump" cases would give them an incentive to prolong or stall lawsuits. Bayer said in a statement that it welcomed the decision, and it "will continue to defend itself against any further efforts by Merck to avoid or improperly transfer its liabilities to Bayer".

COVID-19 vaccine patent litigation

In January 2026, Bayer's Monsanto filed patent infringement lawsuits against Pfizer, BioNTech and Moderna over technology used in the manufacture of their COVID-19 vaccines. The lawsuits, filed in federal court in Delaware, alleged that the companies infringed Monsanto technology developed in the 1980s to reduce the instability of messenger RNA (mRNA) in crops. Monsanto alleged that the vaccine manufacturers used similar methods to stabilize the mRNA in their COVID-19 vaccines.

Bayer separately filed a patent infringement lawsuit against Johnson & Johnson in federal court in New Jersey, alleging that a DNA-based process used in manufacturing its COVID-19 vaccine infringed a Monsanto patent. Bayer sought unspecified monetary damages in the lawsuits but said it was not seeking to prevent the companies from manufacturing their vaccines. Bayer was not involved in developing COVID-19 vaccines and does not manufacture or sell them.