Chapter 36 — Antiviral Pharmacology — Module 4 — Hepatitis B and C Pharmacology
1. [CASE 1 — QUESTION 1]
A 47-year-old man with genotype 1 chronic hepatitis C virus (HCV) infection is referred to begin direct-acting antiviral (DAA) therapy. He has no cirrhosis on elastography, normal renal function, and takes no chronic medications. Before writing for sofosbuvir/velpatasvir, the hepatology team insists on a specific pretreatment screening panel because of a complication that can be fatal during HCV cure. Which screening result would most change the management plan for this patient?
A) A positive hepatitis A immunoglobulin G, indicating prior exposure
B) A normal baseline thyroid-stimulating hormone level
C) A positive hepatitis B surface antigen (HBsAg) with detectable HBV deoxyribonucleic acid (DNA)
D) A normal baseline complete blood count
E) A negative antinuclear antibody titer
ANSWER: C
Rationale:
All patients starting HCV DAA therapy must be screened for HBsAg and antibody to hepatitis B core antigen because clearing HCV can precipitate HBV reactivation, occasionally causing acute liver failure. A positive HBsAg with detectable HBV DNA identifies a patient who needs concomitant HBV-active therapy and would most change the plan.
Option A: Option A is incorrect: prior hepatitis A exposure does not alter HCV DAA management or pose a reactivation risk.
Option B: Option B is incorrect: a normal thyroid-stimulating hormone is relevant to interferon-based therapy, not modern oral DAA regimens, and does not change the plan.
Option D: Option D is incorrect: a normal complete blood count is reassuring but is not the screening result that prevents the fatal complication described.
Option E: Option E is incorrect: a negative antinuclear antibody is unrelated to HBV reactivation risk during HCV therapy.
2. [CASE 1 — QUESTION 2]
Continuing with the same patient. His screening returns HBsAg positive, hepatitis B e antigen (HBeAg) negative, and an HBV deoxyribonucleic acid (DNA) of 1,400 IU/mL. He is otherwise asymptomatic with a normal alanine aminotransferase (ALT). The HCV regimen is still planned. What is the most appropriate hepatitis B management relative to the HCV treatment course?
A) Start tenofovir-based therapy with or before the direct-acting antiviral and continue it for at least 12 weeks after HCV treatment ends
B) Begin the direct-acting antiviral now and add hepatitis B therapy only if HBV DNA rises tenfold
C) Treat the hepatitis B for 4 weeks, then stop it before starting the HCV regimen
D) Give a single dose of hepatitis B immune globulin at HCV initiation
E) Defer HCV therapy until HBsAg becomes undetectable
ANSWER: A
Rationale:
An HBsAg-positive patient is at risk of reactivation when HCV is cleared. Guidelines direct starting tenofovir disoproxil fumarate or tenofovir alafenamide with or before the DAA and continuing it for at least 12 weeks after completing HCV treatment, which provides continuous HBV suppression through the highest-risk window.
Option B: Option B is incorrect: waiting for a tenfold DNA rise risks reactivation hepatitis or liver failure; preemptive therapy is the standard.
Option C: Option C is incorrect: a brief 4-week course that is stopped before HCV therapy leaves the patient unprotected during and after DAA treatment.
Option D: Option D is incorrect: hepatitis B immune globulin is not used to prevent reactivation during DAA therapy; suppressive antiviral therapy is.
Option E: Option E is incorrect: HBsAg rarely clears spontaneously, so deferring HCV care indefinitely is inappropriate when concurrent HBV coverage is available.
3. [CASE 1 — QUESTION 3]
Continuing with the same patient. He is now on tenofovir alafenamide and has completed 12 weeks of sofosbuvir/velpatasvir, with HCV ribonucleic acid (RNA) undetectable at the end of treatment. He asks how the team will confirm he is actually cured of hepatitis C. Which test, at which time point, establishes cure?
A) HCV RNA measured on the last day of treatment
B) Alanine aminotransferase (ALT) normalization at the end of treatment
C) Loss of HCV antibody 12 weeks after treatment
D) HBV DNA suppression at the end of HCV treatment
E) HCV RNA measured 12 weeks after completing treatment, confirming sustained virological response at 12 weeks (SVR12)
ANSWER: E
Rationale:
Cure is defined by sustained virological response at 12 weeks (SVR12): undetectable HCV RNA measured 12 weeks after completing therapy. Because fewer than 1% of patients who reach SVR12 relapse, this post-treatment time point — not the end-of-treatment result — establishes cure.
Option A: Option A is incorrect: undetectable RNA on the last day of treatment is end-of-treatment response, which does not yet confirm cure.
Option B: Option B is incorrect: ALT normalization reflects reduced inflammation but does not define virologic cure.
Option C: Option C is incorrect: HCV antibody typically persists for life and is not used to confirm cure.
Option D: Option D is incorrect: HBV DNA suppression reflects effective hepatitis B therapy, not confirmation of HCV cure.
4. [CASE 1 — QUESTION 4]
Continuing with the same patient. He achieves SVR12 and is delighted. He now asks whether he can stop the tenofovir alafenamide as well, since the hepatitis C is cured and he "feels fine." He remains HBsAg positive. What is the most appropriate counseling?
A) Stop the tenofovir now that the 12-week post-HCV window has passed
B) Continue tenofovir-based therapy because he remains HBsAg positive and chronic hepatitis B generally requires ongoing suppression
C) Switch the tenofovir to lamivudine to reduce long-term cost
D) Stop the tenofovir and recheck HBV DNA only if he develops jaundice
E) Replace the tenofovir with a finite 12-week peginterferon course to complete therapy
ANSWER: B
Rationale:
His hepatitis B is independent of the now-cured hepatitis C. Because he remains HBsAg positive and HBV maintains nuclear covalently closed circular DNA, stopping suppressive therapy would allow viral rebound; chronic HBV generally requires ongoing nucleos(t)ide suppression, so tenofovir should be continued and managed on its own indications.
Option A: Option A is incorrect: the 12-week post-HCV rule governs reactivation prophylaxis timing, not discontinuation of treatment for his underlying chronic hepatitis B.
Option C: Option C is incorrect: lamivudine has a low resistance barrier and is not an appropriate substitute for tenofovir for ongoing suppression.
Option D: Option D is incorrect: waiting for jaundice before rechecking risks a reactivation flare; continued suppression is safer and indicated.
Option E: Option E is incorrect: a finite peginterferon course is not a substitute for ongoing suppression in a patient who needs continued HBV control, and switching has no rationale here.
5. [CASE 2 — QUESTION 1]
A 60-year-old woman with chronic hepatitis B has been maintained on lamivudine for seven years by an outside clinic. Her HBV deoxyribonucleic acid (DNA), long undetectable, has risen to 320,000 IU/mL over the past four months, and her alanine aminotransferase (ALT) is now elevated. Genotypic resistance testing reports rtM204I plus rtL180M. The covering resident is asked to interpret the result. What does this mutational pattern signify?
A) A tenofovir-resistance signature mandating immediate interferon therapy
B) A benign polymorphism unrelated to her rising HBV DNA
C) An entecavir-specific resistance pattern arising independent of prior therapy
D) Lamivudine resistance with virologic breakthrough, the expected consequence of prolonged lamivudine monotherapy
E) Evidence that she was never truly suppressed and is non-adherent
ANSWER: D
Rationale:
The rtM204I (a YMDD-motif substitution) together with the compensatory rtL180M is the classic signature of lamivudine resistance. Paired with a rising HBV DNA after years of suppression, it represents virologic breakthrough — the expected consequence of prolonged lamivudine monotherapy, which selects this pattern in a large fraction of patients over time.
Option A: Option A is incorrect: this is a lamivudine-resistance pattern, not a tenofovir-resistance signature, and interferon is not the mandated response.
Option B: Option B is incorrect: these are clinically significant resistance mutations, not a benign polymorphism, and they explain the rising DNA.
Option C: Option C is incorrect: this pattern reflects lamivudine resistance; entecavir resistance characteristically requires this lamivudine-resistant background plus additional substitutions.
Option E: Option E is incorrect: the data indicate selected resistance under drug pressure, not simply non-adherence, since she was suppressed for years before breakthrough.
6. [CASE 2 — QUESTION 2]
Continuing with the same patient. A colleague suggests switching her from lamivudine to entecavir, reasoning that entecavir normally has a very high resistance barrier. Why is entecavir a poor choice specifically in this patient?
A) Entecavir has no activity against hepatitis B virus in women over 60
B) The pre-existing lamivudine-resistance mutations reduce entecavir binding, so only one or two further substitutions produce high-level entecavir resistance
C) Entecavir cannot be used because it shares cross-resistance with tenofovir
D) Entecavir is contraindicated whenever the HBV DNA exceeds 100,000 IU/mL
E) Entecavir requires an acidic gastric environment that her reflux therapy abolishes
ANSWER: B
Rationale:
Entecavir's high resistance barrier applies to treatment-naive patients. On a lamivudine-resistant background (rtM204I/V plus rtL180M), those substitutions already reduce entecavir binding affinity, so only one or two additional mutations confer high-level entecavir resistance. Entecavir should therefore not be used in patients with known lamivudine resistance.
Option A: Option A is incorrect: entecavir's activity is not abolished by age or sex; the issue is the resistant viral background.
Option C: Option C is incorrect: entecavir does not share cross-resistance with tenofovir; tenofovir in fact retains full activity here.
Option D: Option D is incorrect: there is no HBV DNA threshold that contraindicates entecavir; the problem is the lamivudine-resistant background.
Option E: Option E is incorrect: entecavir absorption is not the issue; the resistance barrier on this mutational background is.
7. [CASE 2 — QUESTION 3]
Continuing with the same patient. Her eGFR is 78 mL/min/1.73m² and she has no bone disease. Given the confirmed lamivudine resistance, which change in therapy is most appropriate?
A) Discontinue lamivudine and switch to tenofovir-based therapy, which retains full activity against lamivudine-resistant hepatitis B virus
B) Continue lamivudine and add entecavir at the standard naive-patient dose
C) Add adefovir dipivoxil to her current lamivudine
D) Switch to telbivudine, which overcomes YMDD-motif mutations
E) Stop all oral therapy and begin peginterferon alfa monotherapy
ANSWER: A
Rationale:
Tenofovir disoproxil fumarate or tenofovir alafenamide retains full activity against lamivudine-resistant HBV and is the preferred switch. With a normal eGFR and no bone disease, either tenofovir formulation is reasonable for ongoing suppression.
Option B: Option B is incorrect: adding standard-dose entecavir on a lamivudine-resistant background risks rapid entecavir resistance, and continuing lamivudine maintains failed pressure.
Option C: Option C is incorrect: adefovir has a low resistance barrier and nephrotoxicity and is not a preferred salvage agent; tenofovir is superior.
Option D: Option D is incorrect: telbivudine shares cross-resistance with lamivudine through the same YMDD-motif mutations and would not overcome them.
Option E: Option E is incorrect: a patient with active virologic breakthrough needs potent suppressive therapy, not a switch to finite peginterferon monotherapy.
8. [CASE 2 — QUESTION 4]
Continuing with the same patient. She is now suppressed on tenofovir and asks what the realistic goal of her therapy is and whether she will ever be able to stop. Which statement best describes the treatment endpoint of oral nucleos(t)ide analogue therapy for her chronic hepatitis B?
A) Eradication of covalently closed circular DNA (cccDNA) within 12 months, after which therapy stops
B) A fixed 48-week course after which the virus is permanently cleared
C) Conversion of the virus to a non-replicating integrated form that no longer requires therapy
D) Complete loss of HBV antibody, signaling cure
E) Sustained viral suppression maintained indefinitely in most patients, because cccDNA persists and HBV DNA rebounds if therapy is discontinued
ANSWER: E
Rationale:
Oral nucleos(t)ide analogues aim for sustained viral suppression, which is maintained indefinitely in most patients. Because cccDNA persists in the hepatocyte nucleus and is not eliminated by these agents, HBV DNA rebounds when therapy is stopped, so suppression is generally lifelong unless HBsAg loss occurs.
Option A: Option A is incorrect: nucleos(t)ide analogues do not eradicate cccDNA, which is precisely why therapy is indefinite.
Option B: Option B is incorrect: there is no fixed finite course that permanently clears HBV with oral suppressive therapy.
Option C: Option C is incorrect: therapy does not convert the virus into a self-limited non-replicating form that frees the patient from treatment.
Option D: Option D is incorrect: loss of HBV antibody is not the endpoint; durable suppression is, and surface antigen loss (not antibody loss) is the rare event that can permit stopping.
9. [CASE 3 — QUESTION 1]
A 55-year-old man with genotype 3 chronic hepatitis C virus infection has compensated cirrhosis (Child-Pugh A) confirmed by transient elastography. He is treatment-naive, has never received a nonstructural protein 5A (NS5A) inhibitor, and has normal renal function. He has no decompensation. Recognizing that genotype 3 with cirrhosis is the most challenging contemporary HCV scenario, which regimen is preferred to maximize his chance of cure where it is available?
A) Sofosbuvir/velpatasvir for 8 weeks
B) Ledipasvir/sofosbuvir for 12 weeks
C) Sofosbuvir/velpatasvir/voxilaprevir for 12 weeks
D) Elbasvir/grazoprevir for 12 weeks
E) Peginterferon plus ribavirin for 24 weeks
ANSWER: C
Rationale:
In genotype 3 with cirrhosis, sofosbuvir/velpatasvir alone achieves only about 88 to 91% sustained virological response — below the rate seen in other populations. Adding the protease inhibitor voxilaprevir as sofosbuvir/velpatasvir/voxilaprevir for 12 weeks is preferred in NS5A-inhibitor-naive genotype 3 cirrhotic patients where available, optimizing the chance of cure.
Option A: Option A is incorrect: an 8-week course is inadequate for genotype 3 with cirrhosis.
Option B: Option B is incorrect: ledipasvir/sofosbuvir has limited activity against genotype 3.
Option D: Option D is incorrect: elbasvir/grazoprevir covers genotypes 1 and 4, not genotype 3.
Option E: Option E is incorrect: interferon-based therapy is obsolete, more toxic, and inferior to direct-acting antiviral regimens here.
10. [CASE 3 — QUESTION 2]
Continuing with the same patient. Before therapy begins, he develops new ascites and an episode of hepatic encephalopathy, and his disease is reclassified as decompensated cirrhosis (Child-Pugh C). How does this change the regimen decision?
A) No change is needed; sofosbuvir/velpatasvir/voxilaprevir remains preferred
B) The dose of voxilaprevir should simply be halved to account for hepatic impairment
C) He should now receive glecaprevir/pibrentasvir, the preferred regimen in decompensation
D) Therapy should be deferred indefinitely because cure is impossible in decompensation
E) Protease-inhibitor-containing regimens, including voxilaprevir, are now contraindicated; sofosbuvir/velpatasvir with or without ribavirin is preferred
ANSWER: E
Rationale:
Decompensated cirrhosis (Child-Pugh B or C) contraindicates NS3/4A protease inhibitors because their concentrations rise dramatically in hepatic impairment, increasing toxicity. The voxilaprevir-containing regimen is therefore no longer appropriate; sofosbuvir/velpatasvir with or without ribavirin for 12 to 24 weeks is preferred, with transplant evaluation in parallel.
Option A: Option A is incorrect: the voxilaprevir-containing regimen becomes contraindicated once the patient is decompensated.
Option B: Option B is incorrect: protease inhibitors are not simply dose-reduced in decompensation; they are contraindicated.
Option C: Option C is incorrect: glecaprevir is itself a protease inhibitor and is contraindicated in decompensated cirrhosis.
Option D: Option D is incorrect: cure remains achievable with a sofosbuvir/velpatasvir-based, protease-inhibitor-free approach alongside transplant evaluation.
11. [CASE 3 — QUESTION 3]
Continuing with the same patient. He is started on sofosbuvir/velpatasvir, and the hepatologist considers adding ribavirin to intensify therapy for his decompensated genotype 3 cirrhosis. His eGFR is normal but his baseline hemoglobin is 10.6 g/dL. What is the most important consideration before adding ribavirin?
A) Ribavirin must be avoided because it is contraindicated with all NS5A inhibitors
B) Ribavirin can intensify therapy but causes dose-dependent hemolytic anemia, so his baseline anemia requires careful monitoring and dose consideration
C) Ribavirin is preferred precisely because it raises hemoglobin during therapy
D) Ribavirin eliminates the need for any sofosbuvir component
E) Ribavirin is renally cleared, so his normal eGFR makes hemolysis impossible
ANSWER: B
Rationale:
Ribavirin can be added to sofosbuvir/velpatasvir to intensify therapy in decompensated cirrhosis, but it causes dose-dependent hemolytic anemia. With a baseline hemoglobin already reduced at 10.6 g/dL, careful monitoring and dose consideration are essential to avoid clinically significant anemia.
Option A: Option A is incorrect: ribavirin is not contraindicated with NS5A inhibitors; it is added selectively, with attention to hemolysis.
Option C: Option C is incorrect: ribavirin lowers hemoglobin through hemolysis rather than raising it.
Option D: Option D is incorrect: ribavirin is an adjunct and does not replace the sofosbuvir backbone.
Option E: Option E is incorrect: normal renal function reduces but does not eliminate hemolytic risk, especially with pre-existing anemia, so hemolysis remains a real concern.
12. [CASE 3 — QUESTION 4]
Continuing with the same patient. He completes therapy and achieves sustained virological response at 12 weeks (SVR12). His liver function improves and he asks whether his cirrhosis-related cancer screening can now be stopped, since the hepatitis C is cured. What is the correct long-term surveillance recommendation?
A) Stop all surveillance, because SVR12 eliminates hepatocellular carcinoma risk
B) Switch to annual HCV ribonucleic acid (RNA) testing in place of imaging
C) Perform a single ultrasound at one year and then discontinue if normal
D) Continue hepatocellular carcinoma surveillance by liver ultrasound every 6 months indefinitely, because risk is reduced but not eliminated in established cirrhosis
E) Begin surveillance only if his alanine aminotransferase (ALT) rises again
ANSWER: D
Rationale:
In patients with established cirrhosis, SVR12 reduces but does not eliminate the risk of hepatocellular carcinoma. Surveillance by liver ultrasound every 6 months should continue indefinitely even after cure, because the cirrhotic liver remains a substrate for malignancy.
Option A: Option A is incorrect: SVR12 lowers but does not abolish hepatocellular carcinoma risk in cirrhosis, so surveillance cannot stop.
Option B: Option B is incorrect: surveillance for cancer uses imaging; HCV RNA testing detects reinfection, not malignancy.
Option C: Option C is incorrect: residual risk is ongoing, so a single normal ultrasound does not justify discontinuation.
Option E: Option E is incorrect: risk persists regardless of ALT, so surveillance is not contingent on enzyme elevation.
13. [CASE 4 — QUESTION 1]
A 44-year-old man with HIV/hepatitis C virus (HCV) co-infection has an undetectable HIV viral load and a CD4 count of 620 cells/mm³ on atazanavir boosted with ritonavir plus tenofovir alafenamide/emtricitabine. He has genotype 1 HCV without cirrhosis and normal renal function. The team plans glecaprevir/pibrentasvir, and the pharmacist immediately flags an interaction. What is the pharmacologic basis of the concern?
A) Glecaprevir is a sensitive cytochrome P450 3A4 (CYP3A4) substrate, and ritonavir-boosted atazanavir raises glecaprevir exposure roughly 6-fold, making the combination contraindicated
B) Glecaprevir induces atazanavir metabolism, risking HIV breakthrough
C) Pibrentasvir chelates atazanavir in the gut, preventing HIV drug absorption
D) Tenofovir alafenamide inactivates glecaprevir through renal competition
E) The combination prolongs the QT interval, requiring electrocardiogram monitoring
ANSWER: A
Rationale:
NS3/4A protease inhibitors such as glecaprevir are sensitive CYP3A4 substrates. Ritonavir-boosted atazanavir inhibits CYP3A4 and raises glecaprevir exposure approximately 6-fold to unsafe levels, so the combination is contraindicated.
Option B: Option B is incorrect: the dangerous direction is increased glecaprevir exposure, not induction lowering atazanavir levels.
Option C: Option C is incorrect: the interaction is CYP3A4-mediated, not gut chelation of atazanavir.
Option D: Option D is incorrect: tenofovir alafenamide does not inactivate glecaprevir by renal competition.
Option E: Option E is incorrect: this is a CYP3A4 exposure interaction, not a shared QT-prolongation effect.
14. [CASE 4 — QUESTION 2]
Continuing with the same patient. The team wants to proceed with glecaprevir/pibrentasvir for his HCV. What is the most appropriate adjustment to his antiretroviral regimen before starting HCV therapy?
A) Halve the glecaprevir/pibrentasvir dose and proceed with atazanavir/ritonavir unchanged
B) Stop the tenofovir alafenamide/emtricitabine backbone for the duration of HCV therapy
C) Add ribavirin to counteract the interaction and continue atazanavir/ritonavir
D) Switch the boosted atazanavir to an integrase inhibitor such as dolutegravir while keeping the tenofovir alafenamide/emtricitabine backbone, then start glecaprevir/pibrentasvir
E) Continue the current regimen and monitor liver enzymes weekly during HCV therapy
ANSWER: D
Rationale:
The interaction is driven by the boosted protease inhibitor. Switching atazanavir/ritonavir to an integrase inhibitor such as dolutegravir — which has minimal interaction with the regimen — while retaining the tenofovir alafenamide/emtricitabine backbone removes the contraindication and continues HIV (and any HBV) coverage, allowing glecaprevir/pibrentasvir to be used safely.
Option A: Option A is incorrect: glecaprevir/pibrentasvir is a fixed-dose combination not designed for dose reduction, and the contraindication would persist.
Option B: Option B is incorrect: stopping the tenofovir backbone removes HIV and HBV protection and does not address the protease-inhibitor interaction.
Option C: Option C is incorrect: ribavirin does not alter this pharmacokinetic interaction.
Option E: Option E is incorrect: the combination is formally contraindicated, so continuing it with monitoring is unsafe.
15. [CASE 4 — QUESTION 3]
Continuing with the same patient. He is now on dolutegravir plus tenofovir alafenamide/emtricitabine with continued HIV suppression, and glecaprevir/pibrentasvir has been started. He asks whether his HIV co-infection lowers his chance of curing the hepatitis C. What is the most accurate response?
A) HIV co-infection roughly halves the chance of HCV cure regardless of treatment
B) HCV cannot be cured while any HIV infection is present
C) With suppressed HIV and a compatible antiretroviral regimen, his sustained virological response rate is equivalent to that of HCV-monoinfected patients
D) His chance of cure depends entirely on his CD4 count exceeding 1,000 cells/mm³
E) Cure requires stopping all antiretroviral therapy during the HCV course
ANSWER: C
Rationale:
With direct-acting antiviral therapy, sustained virological response rates in HIV/HCV co-infected patients are equivalent to those in HCV-monoinfected patients, provided HIV is virologically suppressed and the antiretroviral regimen is compatible with the chosen DAA — both of which are now true for this patient.
Option A: Option A is incorrect: modern DAA therapy does not halve cure rates in co-infection when HIV is suppressed.
Option B: Option B is incorrect: HCV is readily cured in co-infected patients on compatible, suppressive antiretroviral therapy.
Option D: Option D is incorrect: equivalent cure rates do not require a CD4 above 1,000 cells/mm³; virologic suppression and regimen compatibility are what matter.
Option E: Option E is incorrect: antiretroviral therapy is continued, not stopped; interrupting it would jeopardize HIV (and HBV) control.
16. [CASE 4 — QUESTION 4]
Continuing with the same patient. Suppose that, in a counterfactual scenario, the team had instead planned sofosbuvir/velpatasvir and considered switching his antiretroviral anchor to efavirenz. Why would efavirenz be a poor backbone choice with sofosbuvir/velpatasvir, and which agents are preferred instead?
A) Efavirenz raises velpatasvir to toxic levels, while protease inhibitors are preferred
B) Efavirenz has no interaction, so it is fully interchangeable with integrase inhibitors
C) Efavirenz blocks sofosbuvir activation, and boosted atazanavir is the preferred alternative
D) Efavirenz prolongs the QT interval with velpatasvir, and ribavirin is preferred instead
E) Efavirenz reduces sofosbuvir and velpatasvir exposure and is not recommended, whereas dolutegravir, raltegravir, and rilpivirine have minimal interactions and are preferred
ANSWER: E
Rationale:
Efavirenz reduces sofosbuvir and velpatasvir exposure and is not recommended without careful assessment, because subtherapeutic DAA levels risk treatment failure. Dolutegravir, raltegravir, and rilpivirine have minimal interactions with sofosbuvir/velpatasvir and are preferred HIV backbone options during HCV treatment.
Option A: Option A is incorrect: efavirenz lowers, not raises, velpatasvir exposure, and protease inhibitors are not the preferred partners here.
Option B: Option B is incorrect: efavirenz does interact by reducing DAA exposure and is not freely interchangeable.
Option C: Option C is incorrect: the problem is reduced DAA exposure, not blocked sofosbuvir activation, and boosted atazanavir is not preferred.
Option D: Option D is incorrect: the issue is reduced exposure, not QT prolongation, and ribavirin is not a backbone substitute.
17. [CASE 5 — QUESTION 1]
A 63-year-old woman with genotype 1 chronic hepatitis C virus infection has end-stage renal disease and receives maintenance hemodialysis. She has no cirrhosis. Her medication list includes rosuvastatin for hyperlipidemia. The team selects an antiviral regimen with her renal status foremost in mind. Which regimen is preferred, and why?
A) Sofosbuvir/velpatasvir, because hemodialysis reliably clears sofosbuvir metabolites
B) Glecaprevir/pibrentasvir, because both components are biliary-excreted and avoid the renal accumulation that limits sofosbuvir below an eGFR of 30 mL/min/1.73m²
C) Ledipasvir/sofosbuvir, because ledipasvir compensates for impaired sofosbuvir clearance
D) Sofosbuvir monotherapy, because a single renally cleared agent simplifies dialysis dosing
E) Peginterferon plus ribavirin, because neither requires renal dose adjustment
ANSWER: B
Rationale:
In a dialysis patient, glecaprevir/pibrentasvir is preferred because both components are primarily biliary-excreted, avoiding the metabolite accumulation that limits sofosbuvir at very low eGFR. It is approved at standard doses in hemodialysis with high sustained virological response rates.
Option A: Option A is incorrect: reliance on dialysis to clear renally eliminated sofosbuvir metabolites is not the basis for preferring a regimen, and accumulation concerns remain.
Option C: Option C is incorrect: ledipasvir does not correct impaired sofosbuvir clearance, and this combination still contains sofosbuvir.
Option D: Option D is incorrect: sofosbuvir is never used as monotherapy and is renally cleared, making it inappropriate here.
Option E: Option E is incorrect: ribavirin is renally eliminated and causes hemolytic anemia in dialysis, and interferon-based therapy is obsolete.
18. [CASE 5 — QUESTION 2]
Continuing with the same patient. Before starting glecaprevir/pibrentasvir, the team reviews her rosuvastatin. What is the most appropriate action, and what is the mechanism?
A) Discontinue rosuvastatin, because glecaprevir inhibits organic anion transporting polypeptide (OATP) uptake transporters and raises statin concentrations, making rosuvastatin contraindicated
B) Increase the rosuvastatin dose, because glecaprevir induces its metabolism
C) Continue rosuvastatin unchanged, because glecaprevir does not affect statin transporters
D) Switch rosuvastatin to a higher-intensity statin to overcome reduced absorption
E) Replace rosuvastatin with ribavirin to manage lipids during therapy
ANSWER: A
Rationale:
Glecaprevir inhibits the hepatic uptake transporters OATP1B1 and OATP1B3, raising plasma concentrations of statins that depend on them. Rosuvastatin is particularly affected and is contraindicated with glecaprevir/pibrentasvir, so it should be discontinued (other statins require dose limitation).
Option B: Option B is incorrect: glecaprevir raises statin levels via transporter inhibition rather than inducing metabolism, so increasing the dose worsens toxicity risk.
Option C: Option C is incorrect: glecaprevir does affect statin transporters, so continuing rosuvastatin unchanged is unsafe.
Option D: Option D is incorrect: the problem is elevated statin exposure, not reduced absorption, so switching to a higher-intensity statin is exactly wrong.
Option E: Option E is incorrect: ribavirin is not a lipid-lowering agent and has no role in managing her hyperlipidemia.
19. [CASE 5 — QUESTION 3]
Continuing with the same patient. A consultant proposes adding ribavirin to her glecaprevir/pibrentasvir regimen to "be aggressive." Why is ribavirin generally avoided in this dialysis patient?
A) Ribavirin strongly induces P-glycoprotein, lowering glecaprevir levels
B) Ribavirin requires an acidic gastric environment that dialysis abolishes
C) Ribavirin antagonizes pibrentasvir, reducing antiviral activity
D) Ribavirin is renally eliminated and causes hemolytic anemia, a risk that is heightened in dialysis patients
E) Ribavirin is hepatically cleared and accumulates only in hepatic impairment, not renal failure
ANSWER: D
Rationale:
Ribavirin is renally eliminated and causes dose-dependent hemolytic anemia. In dialysis patients, impaired clearance heightens this hemolytic risk, so ribavirin requires dose modification or avoidance and is generally not used. Glecaprevir/pibrentasvir alone is already preferred and effective in this population.
Option A: Option A is incorrect: the concern is renal elimination and hemolysis, not P-glycoprotein induction lowering glecaprevir.
Option B: Option B is incorrect: ribavirin absorption is not the issue; its renal clearance and hemolytic toxicity are.
Option C: Option C is incorrect: ribavirin does not antagonize pibrentasvir; the reason to avoid it is hemolytic anemia.
Option E: Option E is incorrect: ribavirin is renally, not hepatically, eliminated, which is exactly why dialysis patients are at increased risk.
20. [CASE 5 — QUESTION 4]
Continuing with the same patient. Her rosuvastatin has been stopped and ribavirin will not be used. A trainee asks whether the glecaprevir/pibrentasvir dose must be reduced because she is on dialysis. What is the correct answer regarding dosing in severe renal impairment?
A) The dose must be halved on dialysis days only
B) The dose must be reduced by 50% throughout to prevent accumulation
C) No renal dose adjustment is required; glecaprevir/pibrentasvir is given at standard doses in severe renal impairment, including dialysis
D) The dose must be doubled to overcome dialysis clearance of the drug
E) The drug must be given only immediately after each dialysis session at a reduced dose
ANSWER: C
Rationale:
Because glecaprevir and pibrentasvir are biliary-excreted and not renally eliminated, no renal dose adjustment is required. Glecaprevir/pibrentasvir is approved at standard doses across all genotypes in severe renal impairment, including hemodialysis, which is precisely why it is the preferred regimen in this population.
Option A: Option A is incorrect: there is no dialysis-day dose reduction; standard dosing is used.
Option B: Option B is incorrect: a 50% reduction is unnecessary because the drugs are not renally cleared.
Option D: Option D is incorrect: the drug is not appreciably removed by dialysis, so dose doubling is both unnecessary and inappropriate.
Option E: Option E is incorrect: dosing is not tied to dialysis timing, and no reduction is required.
21. [CASE 6 — QUESTION 1]
A 33-year-old woman with hepatitis B e antigen (HBeAg)-positive chronic hepatitis B has HBV genotype A, an alanine aminotransferase (ALT) three times the upper limit of normal, a relatively low HBV deoxyribonucleic acid (DNA) level, and no cirrhosis. She is planning pregnancy in several years and strongly prefers a finite course of therapy with a chance of durable off-treatment control rather than indefinite oral therapy. Which therapy best matches her profile?
A) Lamivudine, because its low resistance barrier suits finite courses
B) Entecavir for 16 weeks followed by discontinuation
C) Adefovir dipivoxil, because it favors HBeAg seroconversion
D) Indefinite tenofovir, because finite therapy is never appropriate in HBeAg-positive disease
E) Peginterferon alfa-2a, because her favorable predictors make durable off-treatment HBeAg seroconversion achievable with a finite course
ANSWER: E
Rationale:
She has several favorable predictors of peginterferon response — genotype A, high baseline ALT, and low baseline HBV DNA — and no contraindication such as cirrhosis. Peginterferon alfa is the only HBV therapy that can induce durable off-treatment responses including HBeAg seroconversion, so a finite peginterferon course fits her profile and her preference.
Option A: Option A is incorrect: lamivudine's low resistance barrier is a liability and it does not provide durable immune-mediated off-treatment control.
Option B: Option B is incorrect: entecavir is a suppressive nucleoside analogue; stopping at 16 weeks would allow viral rebound.
Option C: Option C is incorrect: adefovir is an outdated low-barrier nucleotide analogue, not an immune-based finite therapy.
Option D: Option D is incorrect: finite peginterferon therapy is in fact appropriate for selected HBeAg-positive patients with favorable predictors.
22. [CASE 6 — QUESTION 2]
Continuing with the same patient. She asks how peginterferon works differently from the oral pills her friend takes for hepatitis B. Which description best captures peginterferon's mechanism?
A) It is incorporated into the viral DNA strand and terminates chain elongation
B) It inhibits HBV reverse transcriptase at three distinct steps
C) It combines direct antiviral activity through interferon-stimulated gene induction with immune-modulatory restoration of HBV-specific T-cell responses
D) It permanently eliminates nuclear covalently closed circular DNA (cccDNA)
E) It blocks an HBV protease required for polyprotein maturation
ANSWER: C
Rationale:
Peginterferon alfa acts both directly — inducing interferon-stimulated genes that inhibit HBV replication — and immunologically, restoring HBV-specific T-cell responses. This dual mechanism underlies its capacity to produce durable off-treatment responses, unlike the purely suppressive oral nucleos(t)ide analogues.
Option A: Option A is incorrect: chain termination by incorporation describes nucleos(t)ide analogues such as tenofovir, not peginterferon.
Option B: Option B is incorrect: three-step inhibition of reverse transcription describes entecavir, not peginterferon.
Option D: Option D is incorrect: peginterferon does not eliminate cccDNA; no available HBV agent does.
Option E: Option E is incorrect: HBV does not rely on a protease targeted by peginterferon; peginterferon is immune-based, not a protease inhibitor.
23. [CASE 6 — QUESTION 3]
Continuing with the same patient. Before committing to peginterferon, the team screens for contraindications. Which of the following findings, if present, would most strongly contraindicate peginterferon therapy?
A) A history of poorly controlled major depression with prior suicidal ideation
B) A genotype A hepatitis B virus infection
C) A high baseline alanine aminotransferase (ALT)
D) A low baseline HBV deoxyribonucleic acid (DNA) level
E) Age in the early thirties with plans for future pregnancy
ANSWER: A
Rationale:
Peginterferon is contraindicated in decompensated cirrhosis, autoimmune hepatitis, and psychiatric disorders, given its neuropsychiatric adverse effects. A history of poorly controlled major depression with prior suicidal ideation is a strong contraindication because interferon can precipitate severe neuropsychiatric decompensation.
Option B: Option B is incorrect: genotype A is a favorable predictor of response, not a contraindication.
Option C: Option C is incorrect: high baseline ALT is a favorable response predictor, not a contraindication.
Option D: Option D is incorrect: low baseline HBV DNA is a favorable predictor of response.
Option E: Option E is incorrect: while pregnancy planning warrants counseling, it is not the strong contraindication that active, poorly controlled psychiatric disease represents; therapy would simply be timed and contraception discussed.
24. [CASE 6 — QUESTION 4]
Continuing with the same patient. She has no psychiatric contraindication and proceeds with a 48-week course of peginterferon alfa-2a. She asks what specific result would tell her the finite course succeeded. Which off-treatment outcome best defines a favorable durable response in her HBeAg-positive disease?
A) Permanent eradication of covalently closed circular DNA (cccDNA) documented on liver biopsy
B) HBeAg seroconversion, with sustained off-treatment viral control and, less commonly, hepatitis B surface antigen (HBsAg) loss
C) Loss of hepatitis B core antibody during therapy
D) A transient rise in HBV deoxyribonucleic acid (DNA) at the end of treatment
E) Normalization of the white blood cell count after stopping therapy
ANSWER: B
Rationale:
For HBeAg-positive patients, the favorable durable outcome of finite peginterferon therapy is HBeAg seroconversion with sustained off-treatment viral control; less commonly, patients achieve HBsAg loss, the closest approach to a functional cure. These immune-mediated, durable responses are what distinguish peginterferon from purely suppressive oral therapy.
Option A: Option A is incorrect: peginterferon does not eradicate cccDNA, so this is not an achievable endpoint.
Option C: Option C is incorrect: loss of hepatitis B core antibody is not a treatment endpoint and does not define response.
Option D: Option D is incorrect: a transient HBV DNA rise at end of treatment is not a marker of success.
Option E: Option E is incorrect: white blood cell count normalization reflects recovery from interferon-induced cytopenia, not a virologic treatment response.
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