The FALSE statement is (3) “The only successful gene therapies are those in which cells are removed from a patient, genetically modified, and then reintroduced into patients.”

Option-wise explanation

(1) “Gene therapy involves the direct genetic modification of the cells/model to achieve a therapeutic goal.” – True

Gene therapy is defined as altering the genetic material of cells (adding, correcting, or silencing genes) to treat disease. This can be done ex vivo (cells modified outside the body) or in vivo (vectors injected directly), but in every case it involves direct genetic modification.

(2) “Current gene therapy is directed at modifying somatic cells.” – True

Clinical gene therapy trials almost exclusively target somatic cells (e.g., blood, liver, retinal cells). Germline editing in humans is ethically prohibited in most jurisdictions, so this statement correctly reflects current practice.

(3) “The only successful gene therapies are ex vivo (remove–modify–reintroduce).” – False

While ex vivo approaches (e.g., hematopoietic stem-cell gene therapy for SCID or β‑thalassemia) have been very successful, there are also approved in vivo gene therapies where vectors are delivered directly into patients (e.g., AAV-based therapies injected systemically or into the eye/liver). Successful gene therapy is not limited to ex vivo methods, so this statement is false.

(4) “Recessively inherited disorders are good targets for gene therapy.” – True

For many recessive diseases, pathology arises from loss of function of both alleles. Gene therapy can often help by adding back a functional copy of the gene, without needing to silence a dominant mutant allele. This makes recessive disorders especially amenable to gene addition strategies.

Because successful gene therapy now includes both ex vivo and in vivo treatments, statement (3) is the only false statement.