Chapter 27 — Gastrointestinal Pharmacology — Module 4 — Inflammatory Bowel Disease Pharmacology, Part 2: Biologics and Small Molecules (Tier 1: Foundational Recall)
1. Infliximab binds both soluble and transmembrane TNF-alpha. Beyond simple cytokine neutralization, which transmembrane-TNF–dependent action is believed to contribute specifically to its efficacy in fistulizing Crohn's disease?
A) Selective blockade of the alpha-4-beta-7 integrin on gut-homing lymphocytes
B) Inhibition of Janus kinase (JAK)-STAT signaling within mucosal T cells
C) Activation of reverse signaling through membrane-bound TNF with induction of T-cell apoptosis in the lamina propria
D) Neutralization of the interleukin-23 (IL-23) p19 subunit, reducing Th17 activity
E) Competitive antagonism at the mucosal addressin cell adhesion molecule-1 (MAdCAM-1) receptor
ANSWER: C
Rationale:
Binding to transmembrane TNF-alpha is thought to trigger reverse (outside-to-inside) signaling in the TNF-bearing cell and to induce apoptosis of activated T cells in the lamina propria, a mechanism implicated in infliximab's efficacy against fistulizing Crohn's disease that goes beyond neutralization of soluble cytokine alone.
Option A: Option A describes vedolizumab's integrin blockade, which is unrelated to transmembrane TNF signaling.
Option B: Option B describes the JAK inhibitors, which act intracellularly and are not antibodies that engage membrane TNF.
Option D: Option D describes risankizumab's selective IL-23 p19 blockade, a different pathway entirely.
Option E: Option E misstates the mechanism; MAdCAM-1 is the endothelial ligand engaged by the alpha-4-beta-7 integrin, not a target of infliximab.
2. Certolizumab pegol differs structurally from the other anti-TNF agents in that it is a PEGylated Fab' fragment lacking the fragment crystallizable (Fc) region. Which set of functional consequences follows directly from the absence of the Fc region?
A) It cannot fix complement, cannot mediate antibody-dependent cellular cytotoxicity, and cannot cross the placenta via the neonatal Fc receptor
B) It cannot bind soluble TNF-alpha and therefore acts only on the transmembrane form
C) It is converted to an oral small molecule with hepatic metabolism
D) It acquires gut-selective targeting of the alpha-4-beta-7 integrin
E) It develops markedly higher immunogenicity than chimeric antibodies
ANSWER: A
Rationale:
The Fc region mediates complement fixation, antibody-dependent cellular cytotoxicity, and neonatal Fc receptor–dependent placental transfer. Because certolizumab pegol lacks the Fc region, it does none of these, which is why it is the preferred anti-TNF agent in the third trimester of pregnancy.
Option B: Option B is incorrect; certolizumab still binds soluble and transmembrane TNF-alpha through its Fab' fragment.
Option C: Option C is incorrect because certolizumab remains an injectable antibody fragment, not an oral small molecule.
Option D: Option D is incorrect; the loss of the Fc region does not confer integrin specificity, which is a property of vedolizumab.
Option E: Option E inverts the truth, since the PEGylated humanized fragment is not more immunogenic than a chimeric antibody such as infliximab.
3. A patient with Crohn's disease is to begin infliximab. Which dosing schedule correctly describes standard infliximab induction and maintenance?
A) 160 mg subcutaneously at week 0, 80 mg at week 2, then 40 mg every 2 weeks
B) 10 mg orally twice daily for 8 weeks, then 5 mg twice daily
C) 300 mg intravenously at weeks 0, 2, and 6, then every 8 weeks
D) 5 mg/kg by intravenous infusion at weeks 0, 2, and 6, followed by maintenance infusions every 8 weeks
E) 45 mg orally once daily for induction, then 15 mg once daily for maintenance
ANSWER: D
Rationale:
Infliximab is dosed by weight at 5 mg/kg given as an intravenous infusion at weeks 0, 2, and 6 for induction, followed by maintenance infusions every 8 weeks.
Option A: Option A describes the subcutaneous adalimumab schedule.
Option B: Option B describes a tofacitinib oral regimen, not an antibody infusion.
Option C: Option C describes the fixed 300 mg intravenous dosing of vedolizumab rather than infliximab's weight-based dosing.
Option E: Option E describes an oral upadacitinib schedule, not infliximab.
4. Hepatosplenic T-cell lymphoma is a rare but serious malignancy associated with inflammatory bowel disease therapy. Which patient population and drug exposure carry the characteristic risk?
A) Elderly women on vedolizumab monotherapy
B) Young males on long-term combination anti-TNF plus thiopurine therapy
C) Postmenopausal women on short-course corticosteroids
D) Middle-aged patients on Janus kinase (JAK) inhibitor monotherapy
E) Children on aminosalicylate monotherapy
ANSWER: B
Rationale:
Hepatosplenic T-cell lymphoma has been reported almost exclusively in young males on long-term combination anti-TNF plus thiopurine therapy, and this specific risk informs decisions about whether to continue dual therapy or withdraw the immunomodulator after a period of remission.
Option A: Option A is incorrect; vedolizumab monotherapy is not the agent or population associated with this lymphoma.
Option C: Option C is incorrect because short-course corticosteroids are not linked to hepatosplenic T-cell lymphoma.
Option D: Option D is incorrect; the characteristic association is with combination anti-TNF plus thiopurine, not JAK inhibitor monotherapy.
Option E: Option E is incorrect because aminosalicylate monotherapy does not carry this risk.
5. Pre-biologic screening identifies a patient who is hepatitis B surface antigen (HBsAg)-positive before starting an anti-TNF agent. What is the correct management with respect to hepatitis B?
A) Anti-TNF therapy is absolutely contraindicated for life in any HBsAg-positive patient
B) No specific action is needed because anti-TNF agents do not affect hepatitis B
C) A single dose of hepatitis B vaccine at initiation is sufficient
D) The patient should receive interferon monotherapy instead of any biologic
E) Antiviral prophylaxis should be given throughout biologic therapy and continued for 6 to 12 months after stopping
ANSWER: E
Rationale:
HBsAg-positive patients are at risk of hepatitis B reactivation during immunosuppression, so antiviral prophylaxis must be given throughout biologic therapy and continued for 6 to 12 months after the biologic is stopped.
Option A: Option A is incorrect; HBsAg positivity is not an absolute lifelong contraindication, because reactivation risk can be managed with antiviral prophylaxis.
Option B: Option B is incorrect because anti-TNF–induced immunosuppression can precipitate reactivation.
Option C: Option C is incorrect; vaccination does not protect a patient who is already HBsAg-positive, and a single dose would not be adequate prophylaxis in any case.
Option D: Option D is incorrect because interferon is not the standard substitute, and the issue is reactivation prophylaxis rather than choice of a different immunosuppressant.
6. Among the Janus kinase (JAK) inhibitors used in inflammatory bowel disease, which statement correctly characterizes tofacitinib's selectivity and approved indication?
A) It is a pan-JAK inhibitor with relative selectivity for JAK1 and JAK3 over JAK2, and it is approved for moderate to severe ulcerative colitis
B) It is a selective JAK2 inhibitor approved only for Crohn's disease
C) It is a selective JAK1 inhibitor approved for both ulcerative colitis and Crohn's disease
D) It is a tyrosine kinase 2 (TYK2)-selective inhibitor approved for fistulizing disease
E) It is an injectable JAK inhibitor approved exclusively for extraintestinal manifestations
ANSWER: A
Rationale:
Tofacitinib is a pan-JAK inhibitor with relative selectivity for JAK1 and JAK3 over JAK2, and it is approved for moderate to severe ulcerative colitis, dosed at 10 mg twice daily for induction and 5 mg twice daily for maintenance.
Option B: Option B is incorrect; tofacitinib is not JAK2-selective and is approved for ulcerative colitis rather than Crohn's disease.
Option C: Option C describes upadacitinib, the selective JAK1 inhibitor approved for both indications.
Option D: Option D is incorrect because tofacitinib is not TYK2-selective.
Option E: Option E is incorrect; tofacitinib is an oral agent, not an injectable, and is approved for ulcerative colitis rather than exclusively for extraintestinal manifestations.
7. Upadacitinib's selective Janus kinase 1 (JAK1) inhibition is intended to spare a specific set of adverse effects mediated by Janus kinase 2 (JAK2). Which adverse effects are mediated by JAK2 signaling and therefore reduced by JAK1 selectivity?
A) Herpes zoster reactivation and upper respiratory infections
B) Hyperlipidemia and hepatic transaminase elevation
C) Anemia and neutropenia, because JAK2 transduces erythropoietin and related hematopoietic cytokine signaling
D) Major adverse cardiovascular events and venous thromboembolism
E) Injection-site reactions and infusion reactions
ANSWER: C
Rationale:
JAK2 transduces signaling for erythropoietin and other hematopoietic cytokines, so JAK2 inhibition contributes to anemia and neutropenia; designing upadacitinib for JAK1 selectivity was intended to reduce these JAK2-mediated cytopenias while preserving efficacy.
Option A: Option A is incorrect; herpes zoster reactivation is a class effect of JAK inhibition tied to immune signaling broadly, not a JAK2-specific hematopoietic effect that selectivity removes.
Option B: Option B is incorrect because lipid changes and transaminase elevation are not the JAK2-mediated cytopenias addressed by JAK1 selectivity.
Option D: Option D is incorrect; major adverse cardiovascular events and venous thromboembolism are class-wide black box concerns that JAK1 selectivity does not eliminate.
Option E: Option E is incorrect because injection-site and infusion reactions are features of biologics, not oral JAK inhibitors.
8. A post-marketing safety study comparing a Janus kinase (JAK) inhibitor with TNF inhibitors in older patients with cardiovascular risk factors found higher rates of major adverse cardiovascular events, malignancy, and venous thromboembolism, leading to the class-wide black box warning. Applying that finding, how should JAK inhibitor use be positioned in clinical practice?
A) JAK inhibitors should be used first-line in all patients because oral dosing improves adherence
B) JAK inhibitors should generally be reserved for patients with an inadequate response to or intolerance of one or more TNF inhibitors, with particular caution in patients aged 50 or older who have cardiovascular risk factors
C) JAK inhibitors should be combined routinely with an anti-TNF agent to balance their risks
D) JAK inhibitors are safe to use without cardiovascular assessment in patients under 65
E) JAK inhibitors should replace all biologics in patients with prior venous thromboembolism
ANSWER: B
Rationale:
The safety finding translates directly into positioning: JAK inhibitors should generally be reserved for patients with an inadequate response to or intolerance of one or more TNF inhibitors, with heightened caution in patients aged 50 or older who carry cardiovascular risk factors, the group in which the excess risk was concentrated.
Option A: Option A incorrectly makes JAK inhibitors first-line for everyone, which contradicts the warning.
Option C: Option C incorrectly recommends routine combination with an anti-TNF agent, which compounds immunosuppression and does not mitigate cardiovascular risk.
Option D: Option D is incorrect because cardiovascular risk assessment is required and the threshold of concern begins at age 50, not 65.
Option E: Option E inverts the implication; prior venous thromboembolism is a reason for caution, not an indication to switch to a JAK inhibitor.
9. Compared with anti-TNF agents, vedolizumab has a pharmacodynamic feature that constrains the clinical situations in which it is a good first choice. Which statement correctly describes this feature and its consequence?
A) It has a faster onset than anti-TNF agents, making it the agent of choice for acute severe disease
B) It has identical onset to anti-TNF agents, so onset is not a consideration
C) It produces immediate immunosuppression, which raises early infection risk during induction
D) Its onset of action is slower than anti-TNF agents, particularly in Crohn's disease where weeks 10 to 14 may be needed for meaningful response, which limits its use in acute severe disease
E) Its onset is so rapid that maintenance dosing is unnecessary
ANSWER: D
Rationale:
Vedolizumab acts more slowly than anti-TNF agents, particularly in Crohn's disease, where a meaningful clinical response may not appear until weeks 10 to 14; this slower onset limits its usefulness when rapid control of acute severe disease is required.
Option A: Option A incorrectly states that vedolizumab has a faster onset; vedolizumab is slower, not faster, than anti-TNF agents.
Option B: Option B is incorrect because the onset is not identical; the slower onset is a defining practical difference.
Option C: Option C is incorrect; vedolizumab's gut-selective mechanism does not produce systemic immunosuppression and is associated with a favorable infection profile rather than elevated early infection risk.
Option E: Option E is incorrect because maintenance dosing every 8 weeks is required regardless of onset.
10. Which dosing pattern correctly describes ustekinumab in inflammatory bowel disease?
A) 5 mg/kg intravenously at weeks 0, 2, and 6, then every 8 weeks
B) 40 mg subcutaneously every 2 weeks after a loading dose
C) 10 mg orally twice daily for induction, then 5 mg twice daily
D) 300 mg intravenously at weeks 0, 2, and 6, then every 8 weeks
E) A single weight-based intravenous induction dose of approximately 6 mg/kg, followed by 90 mg subcutaneously every 8 or 12 weeks
ANSWER: E
Rationale:
Ustekinumab is given as a single weight-based intravenous induction dose of approximately 6 mg/kg, followed by 90 mg subcutaneously every 8 or 12 weeks for maintenance.
Option A: Option A describes infliximab's weight-based infusion schedule.
Option B: Option B describes the adalimumab subcutaneous maintenance regimen.
Option C: Option C describes an oral tofacitinib regimen.
Option D: Option D describes vedolizumab's fixed 300 mg intravenous schedule, not ustekinumab.
11. Risankizumab and ustekinumab both target the interleukin-23 (IL-23) axis but differ in the precise subunit they bind. Which statement correctly distinguishes the two?
A) Risankizumab selectively blocks the IL-23 p19 subunit, sparing interleukin-12 (IL-12), whereas ustekinumab binds the p40 subunit shared by IL-12 and IL-23, blocking both cytokines
B) Risankizumab blocks the shared p40 subunit, whereas ustekinumab selectively blocks IL-23 p19
C) Both agents block tumor necrosis factor (TNF)-alpha through the p40 subunit
E) Both agents are Janus kinase (JAK) inhibitors acting on the IL-23 receptor intracellularly
ANSWER: A
Rationale:
Risankizumab selectively blocks the IL-23 p19 subunit and therefore spares IL-12, whereas ustekinumab binds the p40 subunit shared by IL-12 and IL-23 and thus blocks both cytokines.
Option B: Option B reverses the two agents' mechanisms.
Option C: Option C is incorrect because neither agent targets TNF-alpha; the p40 subunit belongs to the IL-12/IL-23 axis.
Option D: Option D is incorrect; the alpha-4-beta-7 integrin is the target of vedolizumab, not risankizumab.
Option E: Option E is incorrect because both agents are monoclonal antibodies acting on extracellular cytokine subunits, not JAK inhibitors.
12. During therapeutic drug monitoring of infliximab maintenance therapy, which trough concentration range is associated with clinical remission?
A) 0.5 to 1 mcg/mL
B) 5 to 12 mcg/mL
C) 3 to 7 mcg/mL
D) 20 to 30 mcg/mL
E) 50 to 100 mcg/mL
ANSWER: C
Rationale:
For infliximab maintenance therapy, trough concentrations of 3 to 7 mcg/mL are associated with clinical remission, and these levels are interpreted alongside inflammatory biomarkers rather than as rigid cutoffs.
Option A: Option A understates the target and would represent subtherapeutic exposure.
Option B: Option B misidentifies the adalimumab target range as the infliximab range, a deliberate discrimination point.
Option D: Option D overstates the target, lying far above the established infliximab maintenance range and not corresponding to the remission-associated trough window.
Option E: Option E overstates the target even further, far above the established infliximab maintenance range and not corresponding to the remission-associated trough window.
13. A patient on maintenance anti-TNF therapy develops secondary loss of response. Testing shows a low trough drug concentration with low or absent anti-drug antibodies. How is this pattern classified, and what is the appropriate management?
A) Immunogenic failure; switch to a different anti-TNF agent
B) Pharmacodynamic failure; switch to a different biologic class
C) Primary non-response; discontinue all advanced therapy
D) Pharmacokinetic failure (drug clearance); manage by dose escalation or shortening the dosing interval
E) Laboratory artifact; repeat the level and make no change
ANSWER: D
Rationale:
A low trough concentration with low or absent anti-drug antibodies indicates pharmacokinetic failure, also called drug clearance; because there is no significant immunogenicity, the appropriate response is to increase the dose or shorten the dosing interval to restore therapeutic trough levels.
Option A: Option A is incorrect because immunogenic failure requires high anti-drug antibodies, which are absent here.
Option B: Option B incorrectly invokes pharmacodynamic failure, which is defined by an adequate trough, not a low one.
Option C: Option C misidentifies secondary loss of response as primary non-response and inappropriately abandons therapy.
Option E: Option E is incorrect because the result is informative and indicates a need to optimize dosing rather than to dismiss the finding.
14. A landmark trial in biologic- and immunomodulator-naive Crohn's disease patients compared infliximab monotherapy, azathioprine monotherapy, and the combination of both. Applying the conclusion of that trial, what should guide initial therapy in an appropriate naive patient?
A) Azathioprine monotherapy produces the highest trough infliximab levels and is preferred alone
B) Combination infliximab plus azathioprine improves outcomes over either agent alone, largely by reducing anti-drug antibody formation and raising infliximab trough concentrations
C) Infliximab monotherapy is superior to combination therapy because it avoids all immunosuppression-related risk
D) The three approaches are equivalent, so cost should be the only deciding factor
E) Combination therapy is inferior because azathioprine accelerates infliximab clearance
ANSWER: B
Rationale:
The trial's conclusion applied to practice is that combination infliximab plus azathioprine improves clinical outcomes over either agent used alone, an effect attributed largely to reduced anti-drug antibody formation and consequently higher infliximab trough concentrations.
Option A: Option A is incorrect because azathioprine monotherapy does not raise infliximab levels and was not the superior arm.
Option C: Option C is incorrect; infliximab monotherapy was not superior to combination therapy, and avoiding immunosuppression entirely is not what the trial showed.
Option D: Option D is incorrect because the arms were not equivalent; combination therapy was superior.
Option E: Option E inverts the mechanism, since azathioprine reduces immunogenicity and tends to raise rather than accelerate clearance of infliximab.
15. A patient with Crohn's disease who is pregnant requires ongoing anti-TNF therapy through the third trimester. Among the anti-TNF agents, which is preferred specifically because of minimal placental transfer, and on what structural basis?
A) Infliximab, because intravenous dosing can be timed to minimize fetal exposure
B) Adalimumab, because its fully human composition prevents transfer
C) Golimumab, because monthly dosing reduces cumulative fetal exposure
D) Any anti-TNF agent equally, because none crosses the placenta
E) Certolizumab pegol, because it lacks the fragment crystallizable (Fc) region and therefore is not transported across the placenta by the neonatal Fc receptor
ANSWER: E
Rationale:
Certolizumab pegol is preferred in the third trimester because its Fab' fragment lacks the Fc region required for neonatal Fc receptor–mediated placental transfer, so minimal drug reaches the fetus.
Option A: Option A is incorrect because infliximab is a complete IgG1 antibody that crosses the placenta in the third trimester regardless of infusion timing.
Option B: Option B is incorrect; adalimumab, although fully human, is a full IgG1 antibody that does transfer across the placenta.
Option C: Option C is incorrect because golimumab is also a full IgG1 antibody and its dosing interval does not prevent transfer.
Option D: Option D is incorrect because the anti-TNF agents are not equivalent in this respect; the full IgG1 antibodies do cross the placenta, whereas certolizumab essentially does not.
16. The treat-to-target principle now guides advanced therapy in inflammatory bowel disease. What is the treatment goal under this principle?
A) Deeper remission, defined as histological remission in ulcerative colitis and transmural (imaging) remission in Crohn's disease, rather than symptom control alone
B) Complete withdrawal of all therapy once symptoms resolve
C) Maintaining the lowest possible drug trough concentration to limit cost
D) Symptom control alone, because endoscopic and histological endpoints do not affect outcomes
E) Permanent corticosteroid maintenance to suppress all inflammation
ANSWER: A
Rationale:
Treat-to-target sets the goal as deeper remission, histological remission in ulcerative colitis and transmural remission assessed by imaging in Crohn's disease, rather than symptom relief alone, because objective mucosal and transmural healing correlates with better long-term outcomes.
Option B: Option B is incorrect; resolution of symptoms does not justify stopping all therapy, and doing so risks relapse.
Option C: Option C is incorrect because the target is defined by disease remission endpoints, not by minimizing trough levels for cost.
Option D: Option D incorrectly treats symptom control as sufficient, which contradicts the treat-to-target principle.
Option E: Option E is incorrect because chronic corticosteroid maintenance is specifically avoided in inflammatory bowel disease due to toxicity and is not a treat-to-target strategy.
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