**Core Concept**
Orphan drugs are medications or treatments developed for rare diseases or conditions that affect a small percentage of the population. These drugs are often designed to target specific genetic mutations or molecular pathways associated with these rare conditions.

**Why the Correct Answer is Right**
Orphan drugs are designated by regulatory agencies such as the FDA in the US or the EMA in Europe to provide incentives for their development, including tax credits, grants, and market exclusivity. This designation is typically reserved for medications that treat conditions affecting fewer than 200,000 people in the US or 5 in 10,000 people in the EU. The development of orphan drugs often involves a multidisciplinary approach, including geneticists, molecular biologists, and clinicians working together to identify and validate potential therapeutic targets.

**Why Each Wrong Option is Incorrect**
**Option A:** This option does not accurately describe an orphan drug. While some orphan drugs may be developed by small biotechnology companies, this is not a defining characteristic of orphan drugs in general.
**Option B:** This option is incorrect because orphan drugs are not necessarily more expensive than other medications. In fact, many orphan drugs are designed to be cost-effective and accessible to patients.
**Option C:** This option is not accurate because orphan drugs are not limited to genetic disorders. While some orphan drugs do target genetic mutations, others may target molecular pathways or cellular processes associated with rare conditions.

**Clinical Pearl / High-Yield Fact**
One key aspect of orphan drug development is the need for a strong scientific rationale and a well-defined target population. This often involves collaboration between clinicians, researchers, and industry partners to identify potential therapeutic targets and develop effective treatments for rare conditions.

**Correct Answer:** D.