Biology • Year 12 • Module 6 • Lesson 10
Future Directions and Potential Benefits for Society
Apply the lesson's need × feasibility × fairness framework to three real, current biotechnology case studies — gene therapy (Casgevy), CAR-T cell therapy, and gene drives in mosquito populations — and to a real cost / access dataset.
1. Case study — gene therapy: Casgevy (CRISPR) for sickle cell disease
Stimulus. In late 2023 the UK Medicines and Healthcare products Regulatory Agency, and then the US FDA, approved Casgevy (exagamglogene autotemcel) for sickle cell disease and transfusion-dependent beta-thalassaemia. Casgevy is the first approved therapy that uses CRISPR/Cas9 gene editing. Patients' own haematopoietic stem cells are removed, the BCL11A regulatory enhancer is edited ex vivo to re-activate fetal haemoglobin, and the modified cells are re-infused after the patient undergoes high-dose chemotherapy. The published list price in the United States is approximately US$2.2 million per patient; the treatment is currently delivered at a small number of specialised centres, requires weeks of inpatient care, and there is an ongoing 15-year follow-up requirement to monitor safety, including possible off-target edits.
1.1 Identify which of the lesson's four emerging biotechnology directions (gene editing, synthetic biology, precision breeding, disease screening) Casgevy is an example of, and justify your choice in one sentence. 2 marks
1.2 Using the lesson's need × feasibility × fairness framework, evaluate Casgevy as a future direction for sickle cell disease. Write one short sentence under each heading. 6 marks (2 each)
Need:
Feasibility:
Fairness:
1.3 A media headline reads: "CRISPR cures genetic disease — sickle cell is over." Identify one way this headline overclaims, and rewrite it using evidence-based language from the lesson. 3 marks
2. Case study — CAR-T cell therapy for blood cancers
Stimulus. CAR-T (Chimeric Antigen Receptor T-cell) therapies such as Kymriah (tisagenlecleucel) and Yescarta (axicabtagene ciloleucel) are approved targeted therapies for certain B-cell leukaemias and lymphomas. A patient's own T cells are collected, genetically modified ex vivo to express a synthetic receptor that recognises the CD19 antigen on B cells, expanded, and re-infused. In pivotal trials, complete response rates in heavily pre-treated paediatric B-cell ALL exceeded 80%, far above historical chemotherapy outcomes. However, CAR-T does not work for solid tumours yet, costs roughly US$370,000–$475,000 per infusion (before hospital costs), and serious side-effects include cytokine release syndrome and neurotoxicity, requiring intensive-care–capable centres.
2.1 Explain how CAR-T cell therapy fits the lesson's definition of a targeted therapy. Use one specific molecular detail from the stimulus. 2 marks
2.2 A student writes: "Because CAR-T works in B-cell leukaemia, all cancers will soon be cured by CAR-T." Identify two specific reasons (from the stimulus and from the lesson) why this overclaims, and rewrite the statement using cautious, evidence-based language. 4 marks (1 + 1 + 2)
Reason 1:
Reason 2:
Rewritten statement:
2.3 Using the lesson's framework, predict one realistic social benefit that CAR-T could deliver over the next decade and one barrier that would have to be solved first. 3 marks
Realistic benefit:
Barrier:
3. Case study — gene drives to suppress malaria-vector mosquitoes
Stimulus. A gene drive is a CRISPR-based genetic element engineered so that, after fertilisation, it copies itself onto the second chromosome of the offspring. As a result, almost all offspring inherit the drive — far above the 50% that ordinary inheritance would give. The Target Malaria consortium has developed a gene drive in Anopheles gambiae (a major malaria vector) that disrupts the doublesex female-fertility gene. Cage-trial populations were driven to extinction within ~7–11 generations. Field release has not yet been authorised anywhere in the world, because (a) once released, the drive cannot easily be recalled, (b) it could spread across borders without consent, and (c) eliminating one vector species could have unpredictable ecological effects on predators and competing species. Malaria still kills an estimated 600,000 people per year, predominantly children under five in sub-Saharan Africa.
3.1 Which two emerging biotechnology directions from Card 1 best describe gene drives? Justify in one sentence. 2 marks
3.2 Use the lesson's need × feasibility × fairness framework to evaluate the proposed field release of Anopheles gambiae gene drives. 6 marks (2 each)
Need:
Feasibility:
Fairness:
3.3 Why is the gene-drive case a particularly clear illustration of the lesson's claim that "current capability is not the same as future direction"? Answer in 2–3 sentences. 3 marks
4. Interpret the data — list price of approved gene therapies
The bar chart shows the published list prices (US$ millions) of the first commercially approved gene or cell therapies in the United States, alongside an estimate of the typical median household income (~US$80,000 in 2023). The data are real and verifiable from the FDA / manufacturer announcements. 7 marks
4.1 Describe the overall pattern in list prices across the seven therapies. Quote at least one supporting figure. 2 marks
4.2 Approximately how many years of median US household income would be required to pay the published list price of Hemgenix (haemophilia B)? Show your working. 2 marks
4.3 Use the data to argue, in the lesson's vocabulary, why fairness (rather than just feasibility) is the binding constraint on whether these biotechnologies translate into broad social benefit. 3 marks
Q1 — Casgevy / sickle cell (11 marks total)
1.1 (2 marks). Casgevy is a gene-editing therapy (CRISPR/Cas9) [1]; it makes a targeted change to the BCL11A regulatory enhancer in the patient's own haematopoietic stem cells, which fits the Key Terms definition of "targeted alteration of DNA sequence at a chosen location" [1]. Also accept "targeted therapy" as a secondary classification, since the genetic change targets a specific regulatory element.
1.2 (6 marks).
Need (2): Sickle cell disease causes severe pain, organ damage and reduced life expectancy, and existing therapies (transfusion, hydroxyurea, allogeneic bone marrow transplant) are partial or require an HLA-matched donor [1]. A durable single-treatment option therefore addresses a real, well-documented clinical need [1].
Feasibility (2): Casgevy has now passed regulatory approval in the UK and US, so safety/efficacy is supported by trial evidence [1]. However it requires ex vivo editing, high-dose chemotherapy conditioning, specialised centres, and 15-year safety follow-up for off-target effects, so it is not yet feasible at population scale [1].
Fairness (2): At ~US$2.2 million per patient and limited treatment-centre capacity, access is concentrated in wealthy health systems [1] — but sickle cell disease is most prevalent in sub-Saharan Africa and among diaspora populations, so without subsidy or technology transfer the benefit reaches a small fraction of those who need it [1].
1.3 (3 marks). The headline overclaims because (a) Casgevy is approved, not "the end of sickle cell" — eligibility is restricted, follow-up is ongoing, off-target risk is not yet closed out, and access is severely limited by cost and geography [1 + 1]. Rewrite: "A CRISPR-based therapy (Casgevy) has been approved for sickle cell disease and may benefit patients who can access it, although long-term safety, cost and equitable access remain to be established." [1]
Q2 — CAR-T cell therapy (9 marks)
2.1 (2 marks). CAR-T is a targeted therapy because the engineered chimeric antigen receptor specifically recognises the CD19 antigen on B cells [1], so the modified T cells attack CD19-positive cancer cells rather than affecting all dividing cells, unlike conventional cytotoxic chemotherapy [1].
2.2 (4 marks).
Reason 1 (1): CAR-T currently works against blood cancers expressing CD19; it does not yet work for solid tumours, which behave biologically very differently (hostile tumour microenvironment, heterogeneous antigens).
Reason 2 (1): Cost (~US$370k–$475k per infusion), the need for ICU-capable centres and serious side-effects (cytokine release syndrome, neurotoxicity) limit scalable access — so "all cancers will soon be cured" ignores feasibility and fairness.
Rewritten (2): "CAR-T therapy has produced major improvements in some B-cell leukaemias and lymphomas and could expand to other haematological cancers if antigen targets, safety and cost can be addressed; it is not currently effective against solid tumours."
2.3 (3 marks). Realistic benefit (1): over the next decade, off-the-shelf or allogeneic CAR-T products may bring down cost and turnaround time, expanding access for relapsed/refractory B-cell cancers. Barrier (2): solid tumours remain unsolved due to lack of clean tumour-specific antigens and an immunosuppressive microenvironment [1]; manufacturing cost and ICU-grade infrastructure must come down before benefit can scale beyond high-income settings [1].
Q3 — Gene drives / mosquitoes (11 marks)
3.1 (2 marks). Gene drives combine gene editing (CRISPR-based) and synthetic biology (a deliberately designed inheritance system) [1 + 1] — they are an engineered biological device built around a precise DNA-cutting tool.
3.2 (6 marks).
Need (2): Malaria still kills ~600,000 people per year, mostly children under five in sub-Saharan Africa [1]; existing tools (bed nets, insecticides, antimalarials) have stalled and insecticide resistance is rising, so the need for new interventions is genuine and well-documented [1].
Feasibility (2): The drive works in cage trials — Anopheles gambiae cage populations collapsed within 7–11 generations [1]. However field release is not yet authorised because (a) the drive cannot easily be recalled once released, (b) it could spread across national borders, (c) ecological effects of removing a vector species are unpredictable [1].
Fairness (2): Decisions about field release affect African communities most directly; meaningful consent, governance and benefit-sharing across borders are central to whether release is fair [1]. Fairness also includes who carries the ecological risk if the drive has unintended effects [1].
3.3 (3 marks). Gene drives demonstrate the lesson's claim very directly: the technology has been shown to work in caged populations (current capability is real) [1], but realistic future direction depends on safety, recallability, cross-border governance and ecological assessment, none of which have been resolved [1]. So even though the science exists, the social benefit is not yet a defensible prediction — it is currently a candidate future direction, not an achieved outcome [1].
Q4 — Gene-therapy price data (7 marks)
4.1 (2 marks). All seven approved therapies cost between approximately US$0.37 million (Yescarta) and US$3.5 million (Hemgenix) — orders of magnitude above the ~US$0.08 million median US household income reference line [1]. The CRISPR therapy (Casgevy, $2.2m) sits in the upper range alongside Zolgensma ($2.125m), Elevidys ($3.2m) and Hemgenix ($3.5m) [1].
4.2 (2 marks). US$3,500,000 ÷ US$80,000 per year ≈ 43.75 years of median household income [1 for the calculation, 1 for the correct figure ≈ 44 years]. Accept any value 40–45 with working shown.
4.3 (3 marks). All seven products have demonstrated feasibility — they have passed FDA approval, which means evidence of safety and efficacy exists [1]. So the binding constraint on broad social benefit is no longer "does it work?" but "who can pay for it, who can access the specialised centres that deliver it, and who is reimbursed by their health system?" — i.e. fairness of access [1]. The lesson's framework predicts exactly this: approval establishes feasibility, but if access is unequal the social benefit remains concentrated in a small population, even when the technology itself is real [1].