Facts of the Case:
Sun Pharmaceutical Laboratories Ltd. (SUN) filed a suit against Hetero Healthcare Ltd. (HETERO), alleging trademark infringement and passing off. SUN claimed to be one of the largest generic medicine manufacturers and had registered the trademark 'LETROZ' for its generic drug containing the active ingredient 'LETROZOLE.' HETERO was manufacturing a similar drug under the trademark 'LETERO.'

SUN sought a permanent injunction restraining HETERO from using the trademark 'LETERO,' claiming it was deceptively similar to their registered trademark. The Commercial Court dismissed SUN's application for an injunction, stating that there was no deceptive similarity between the trademarks and the prices of the medicines were significantly different.

Court and Bench:
The case was heard in the High Court of Delhi by Hon'ble Mr. Justice Vibhu Bakhru and Hon'ble Mr. Justice Amit Mahajan.

Issues Involved:
The key issues in this case were:

• Whether SUN was entitled to a permanent injunction restraining HETERO from using the trademark 'LETERO.'
• Whether HETERO's use of the trademark 'LETERO' infringed upon SUN's registered trademark 'LETROZ' and amounted to passing off.

Petitioner's Argument:
SUN argued that it had exclusive rights to the registered trademark 'LETROZ' and that HETERO's use of the similar mark 'LETERO' constituted trademark infringement and passing off. SUN claimed that it had acquired immense reputation and goodwill in the trademark 'LETROZ' and that HETERO's actions were causing confusion among consumers.

Respondent's Argument:
HETERO contended that the word 'LETROZ' was derived from the international non-proprietary name (INN) 'LETROZOLE,' which is a common practice in the pharmaceutical industry. HETERO argued that SUN could not claim a monopoly on the use of the word 'LETROZ' and that their mark 'LETERO' was distinctively different. They also claimed that SUN was aware of HETERO's use of the mark since 2007 and had acquiesced to it.

Principle:
The court referred to Section 13 of the Trade Marks Act, 1999, which states that a word deceptively similar to an international non-proprietary name (INN) declared by the World Health Organization cannot be registered as a trademark. The court considered whether SUN's trademark 'LETROZ' was deceptively similar to the INN 'LETROZOLE' and whether SUN's registration entitled them to exclusive rights over the word 'LETROZ.'

Analysis:
The court analyzed the arguments presented by both parties and examined the similarity between the trademarks 'LETROZ' and 'LETERO.' It considered the phonetic, visual, and structural aspects of the marks and their potential to cause confusion among consumers. The court also reviewed the pricing and packaging of the medicines and the specialized nature of the drug, which required a doctor's prescription. It examined precedents in similar cases and assessed the balance of convenience.

Comment:
The court concluded that SUN's trademark 'LETROZ' was merely the first six letters of the international non-proprietary name 'LETROZOLE.' It found no deceptive similarity between the trademarks and no likelihood of confusion among consumers. The court also considered the difference in pricing and the distinctiveness of HETERO's mark 'LETERO.' Consequently, the court dismissed SUN's application for an injunction, stating that no prima facie case was made out in favor of SUN.