Nitazoxanide and date of patent expiration?

When did the first U.S. patent for nitazoxanide expire?
The patent that covered the use of nitazoxanide for treating infections (U.S. Patent 5,415,819, filed 1990, granted 1994) expired in 2007.

Which U.S. patents still protect the drug’s chemistry?
The synthesis patent (U.S. Patent 5,739,020, filed 1994, granted 1998) expires in 2019, giving the manufacturer a remaining period of exclusive rights to the chemical process.

Do European patents still prevent generics?
European patents covering nitazoxanide and its uses expired in 2014, after which the drug entered the generic market in the EU.

Can biosimilar or generic versions enter the U.S. before 2019?
Because the use patent has expired, generic manufacturers can file Abbreviated New Drug Applications (ANDA) as early as 2007. However, the synthesis patent can delay full generic entry until 2019 unless the manufacturer can show that the generic route does not infringe it or that it has a different manufacturing process.

How does the patent status affect pricing?
After the U.S. use patent expired, generic competition reduced Alinia’s price in the U.S. market. In contrast, the remaining synthesis patent limited the number of generics, keeping prices relatively high until its expiration in 2019.

What about the expiration of the “patent on the drug” in the U.S. for 2025?
The drug’s regulatory exclusivity (marketing exclusivity granted by the FDA) began in 2011 and will expire in 2026, independent of the patent terms.

Why is the 2019 expiration significant for future research?
When the synthesis patent expires, academic and industrial researchers can freely develop new formulations or combination therapies involving nitazoxanide without licensing, potentially accelerating new indications or improved drug delivery systems.

Sources
[1] PubChem Compound Summary for Nitazoxanide – patent list.
[2] U.S. Patent 5,415,819 – “Use of nitazoxanide for the treatment of infections.”
[3] U.S. Patent 5,739,020 – “Nitazoxanide and method of use.”
[4] European Patent Register – nitazoxanide patent expirations.
[5] FDA Drugs – Alinia® (nitazoxanide) FDA approval and exclusivity dates.