BIIB vs ZTS Comparison

Biogen is an established biopharmaceutical company focused on treatments for neurodegenerative and rare diseases. Its declining multiple sclerosis franchise is its largest revenue generator and contributed 40% of total revenue in 2025. Biogen also generates significant revenue from its CD20 collaboration agreements with Roche (19% of total in 2025), which includes oncology drugs Rituxan and Gazyva and multiple sclerosis drug Ocrevus. Biogen's newer franchises include Spinraza (spinal muscular atrophy, with partner Ionis), Leqembi (Alzheimer's disease, collabroation revenue from its partner Eisai), Skyclarys (Friedreich's ataxia, Reata), Zurzuvae (postpartum depression, Sage), and Qalsody (amyotrophic lateral sclerosis, Ionis).

Zoetis sells anti-infectives, vaccines, parasiticides, diagnostics, and other health products for animals. The firm earns roughly 35% of total revenue from production animals (cattle, pigs, poultry, and so on) and nearly 65% from companion animal (dogs, horses, cats) products. Its US business is skewed even more heavily toward companion animals, while its international business is slightly skewed toward production animals. The firm has the largest market share in the industry and was previously Pfizer's animal health unit.