[7] Founded in 1997,[8] it listed on the Johannesburg Stock Exchange (JSE) in 1998,[9] and purchased South African Druggists in 1999 before expanding into international markets.

[10] Currently the largest pharmaceutical company in Africa[11] through aggressive mergers and expansion,[7][12] with major manufacturing sites in locations such as Gqeberha in South Africa,[10] Bad Oldesloe in Germany,[13] Notre-Dame-de-Bondeville in France,[14] and Oss, Netherlands,[15] Aspen is known for manufacturing and distributing branded pharmaceuticals as well as generic HIV/AIDS antiretrovirals (ARVs)[16][10] and cancer medications.

[9] Separate from Lennon, the originating Aspen company was founded in 1997[8] by South African businesspeople Stephen Saad, Gus Attridge, and Steve Sturlese,[10] as well as a fourth shareholder.

[9] Also in 2001, Saad negotiated the "first-ever voluntary" licenses to manufacture generic versions of antiretrovirals (ARVs) to treat HIV, ending a "stand off" between the South African government and various multinational drug companies[10] over anticompetitive activities.

Also, Aspen increased its production to fulfill the President's Emergency Plan for AIDS Relief (PEPFAR) orders from the United States.

[31] In 2013, Aspen announced it would acquire drug brands from MSD[9] and an active pharmaceutical ingredient (API) company in the Netherlands[21] as well as anticoagulant rights.

In 2016 it bought intellectual property and manufacturing rights for Astra Zeneca's anaesthetics,[9] and GSK sold its stake in Aspen in October 2016.

A joint paper on the matter was published in the European Thyroid Journal with recommendations such as reevaluating methods used to determine "the bioequivalence of levothyroxine preparations".

[47] After worries that the vaccine fill stock made by an Emergent BioSolutions plant in Baltimore might have been contaminated, that year Aspen destroyed some of its doses.

In August 2021, Aspen filled vaccine stock from a plant in the Netherlands, with 40% of those doses supposed to go to Europe and the remaining 60% to Africa through the end of September.

[46] Aspen agreed to sell several products, all of which were sold in South Africa,[48] to the Swiss company Acino Pharma AG in October 2021.

[19] Aspen concluded an agreement with Serum Institute of India in August 2022 to manufacture, market and distribute four Aspen-branded routine vaccines for Africa,[54] and received grant funding from the Bill & Melinda Gates Foundation and the Coalition for Epidemic Preparedness Innovations.

[59] In October 2016,[60][61] Aspen was fined $5.5 million[60][61] by the Italian Competition Authority for price hikes[59] initiated between 2012 and 2014[17] in respect to certain cancer drugs.

[59] Aspen unsuccessfully[62] appealed the ruling,[59] arguing that while the hikes appeared large, they resulted from "a very low and unsustainable price base.

"[63] By 2016 Aspen was also being accused of the same practices, including artificially restricting supply, in the United Kingdom, Australia, New Zealand, Spain, France, Brazil,[17] and South Africa.

[72] The commission found that from 2012 to 2019, Aspen had in the EEA persistently earned high profits with its average prices "exceeding costs by almost 300%" for products that had been off-patent for about 50 year.

In order to prevent any further abuse of a dominant position, if Aspen intended to discontinue its supplies, the company must inform any concerned member states at least one year in advance, as well as making EU marketing authorizations for the products available for any interested third party to acquire.