On February 10, 2006, WLF wrote to FDA’s OCBQ, calling on it to withdraw an untitled letter sent to ZLB Behring on February 3 regarding ZLB’s allegedly improper promotion of Rhophylac. Rhophylac is a biologic used to suppress Rh isoimmunization in certain pregnant women. WLF’s letter alleged that OCBQ lacks any basis for its allegation that ZLB Behring’s superiority claims are unsubstantiated. OCBQ argued that ZLB had failed to substantiate its superiority claims by reference to well-controlled clinical studies. WLF responded that insistence on “well-controlled” studies before permitting comparative claims violates both administrative law (because FDA failed to follow requisite notice-and-comment procedures before adopting that rule) and the First Amendment. WLF argued that FDA may not completely bar claims based on the findings of less rigorous studies; rather, if there is support for the superiority claims, FDA may do no more than require that disclaimers accompany the claims.