Physician FamiliarityNarrow moat

An underappreciated but genuine advantage in the incretin market is physician familiarity — the tendency of doctors to reach first for the drug they know, trust, and have prescribed successfully many times. Lilly's early lead and heavy investment in educating prescribers built deep familiarity with tirzepatide among the physicians who treat diabetes and obesity, and that habit and comfort is a real form of stickiness: a doctor confident in a drug's results and safety, with experience managing it, does not lightly switch to an unproven alternative.

The familiarity compounds the first-and-best lead into something stickier than efficacy data alone. Prescribing is a matter of trust and routine as much as of comparison; a physician with hundreds of patients doing well on a Lilly drug has little reason to change, and the accumulated real-world experience — how the drug behaves, how to dose it, how to manage side effects — makes the incumbent the path of least resistance. This inertia, spread across the medical community, protects a franchise well beyond its raw clinical merits.

The limit is that physician familiarity, while real, is not a strong moat on its own and yields to sufficiently superior alternatives or aggressive competitive marketing. Doctors do adopt genuinely better drugs, rivals invest heavily to build their own familiarity, and in a class evolving as fast as the incretins, prescriber habits can shift within a few years. So physician familiarity is a genuine supporting advantage that reinforces Lilly's lead and slows switching, but it is reinforcement for the harder advantages of efficacy — tirzepatide's superior comparative weight loss¹ — and being first, not a foundation that could hold on its own.