Chapter 34 — Anti-Cancer Drugs Part 2 — Module 3 — Monoclonal Antibodies and Antibody-Drug Conjugates
1. A 70-year-old man with metastatic colorectal cancer has moderate hepatic impairment, stage 3 chronic kidney disease, and is taking multiple medications metabolized by hepatic cytochrome P450 (CYP, the liver enzyme family that metabolizes most small-molecule drugs). He is to receive a full-length immunoglobulin G monoclonal antibody. Integrating the absorption, distribution, metabolism, and excretion features of monoclonal antibodies, which overall conclusion about dosing and interactions is correct?
A) The antibody dose must be reduced for hepatic impairment and again for renal impairment, and major CYP-based interactions are expected
B) Renal impairment mandates a large dose reduction because intact antibody is eliminated by glomerular filtration
C) No dose adjustment is generally required for either hepatic or renal impairment, and clinically significant CYP-based, P-glycoprotein, and renal-transporter interactions are not expected, because the antibody is catabolized to amino acids rather than handled by CYP enzymes or excreted intact by the kidney
D) Hepatic impairment requires therapeutic drug monitoring because the liver is the dominant site of intact antibody clearance
E) The antibody will markedly inhibit the patient's CYP enzymes, requiring reduction of his concurrent small-molecule drugs
ANSWER: C
Rationale:
Full-length immunoglobulin G antibodies are catabolized by widespread proteolysis to amino acids, are not CYP substrates, and are too large for meaningful renal excretion of intact antibody. Integrating these features, neither hepatic nor renal impairment generally requires dose adjustment, and the CYP-based, P-glycoprotein, and renal-transporter interactions that complicate small-molecule oncology drugs are not expected.
Option A: Option A is incorrect because neither organ impairment generally mandates dose reduction and major CYP interactions are not anticipated.
Option B: Option B is incorrect because intact antibody is not cleared by glomerular filtration given its large size.
Option D: Option D is incorrect because the liver is not the dominant site of intact antibody clearance and routine therapeutic drug monitoring for hepatic impairment is not required.
Option E: Option E is incorrect because antibodies do not inhibit patient CYP enzymes, so concurrent small-molecule doses do not need reduction on that basis.
2. A patient with HER2-positive (human epidermal growth factor receptor 2-positive) early breast cancer has a baseline left ventricular ejection fraction (LVEF, the percentage of blood ejected from the left ventricle per beat) of 60 percent. She is to receive doxorubicin-cyclophosphamide followed by trastuzumab. Midway through trastuzumab, her LVEF is 46 percent. Integrating the sequencing rule and the cardiac monitoring rule, which management plan is correct?
A) Anthracycline and trastuzumab should be given sequentially (not concurrently) because of additive cardiotoxicity; and because her LVEF has now fallen below 50 percent, trastuzumab should be held with LVEF reassessment, with reinitiation after recovery in most cases
B) The two drugs should have been given concurrently for synergy, and the current LVEF of 46 percent requires no action
C) Trastuzumab should be permanently discontinued immediately on this first qualifying LVEF measurement without any reassessment
D) The anthracycline should be restarted concurrently with trastuzumab to improve tumor control despite the LVEF decline
E) No monitoring is needed because trastuzumab cardiotoxicity is irreversible and unrelated to LVEF
ANSWER: A
Rationale:
Two principles combine here. First, anthracycline and trastuzumab are given sequentially rather than concurrently because concurrent use produces unacceptable rates of symptomatic heart failure. Second, trastuzumab is held when the LVEF falls below 50 percent (or drops 16 or more percentage points), with reassessment and reinitiation in most cases after recovery; permanent discontinuation is reserved for persistent decline after hold-and-reassess cycles. An LVEF of 46 percent meets the hold threshold.
Option B: Option B is incorrect because concurrent administration is contraindicated and a sub-50 percent LVEF does require action.
Option C: Option C is incorrect because the first qualifying measurement triggers holding and reassessment, not immediate permanent discontinuation.
Option D: Option D is incorrect because restarting the anthracycline concurrently would compound cardiotoxicity.
Option E: Option E is incorrect because trastuzumab cardiotoxicity is largely reversible and LVEF monitoring is mandatory.
3. A patient on bevacizumab (an anti-VEGF [vascular endothelial growth factor] antibody with a half-life of approximately 20 days) for metastatic colorectal cancer needs elective bowel surgery. Integrating the drug's mechanism, half-life, and surgical-risk profile, which plan best reflects correct perioperative management?
A) Bevacizumab may be continued up to the day of surgery because its short half-life clears the anti-angiogenic effect within 24 hours
B) Bevacizumab should be held for at least 28 days before surgery and not resumed until at least 28 days after surgery with healing confirmed, because its anti-VEGF effect impairs wound healing and raises the risk of dehiscence, anastomotic leak, and bowel perforation, and its long half-life means the effect persists well beyond a single day
C) Bevacizumab should be stopped only 48 hours before surgery, which is sufficient given anti-VEGF pharmacology
D) Bevacizumab should be permanently discontinued because any elective surgery is an absolute lifelong contraindication to anti-VEGF therapy
E) An extra dose of bevacizumab should be given on the morning of surgery to support anastomotic angiogenesis
ANSWER: B
Rationale:
VEGF-driven angiogenesis is required for wound healing, so bevacizumab impairs healing and raises the risk of dehiscence, anastomotic leak, and bowel perforation. Because its half-life is roughly 20 days, the anti-angiogenic effect persists far beyond a single day, so the drug must be held at least 28 days before elective surgery and not resumed until at least 28 days afterward with healing confirmed.
Option A: Option A is incorrect because the half-life is long (about 20 days), not short, so the effect does not clear within a day.
Option C: Option C is incorrect because a 48-hour hold is far too short given the prolonged effect.
Option D: Option D is incorrect because surgery is not a permanent contraindication; therapy resumes after adequate healing.
Option E: Option E is incorrect because additional bevacizumab around surgery would worsen, not support, anastomotic healing.
4. A patient with metastatic colorectal cancer is being evaluated for cetuximab (an anti-EGFR [epidermal growth factor receptor] antibody). The tumor is RAS (rat sarcoma proto-oncogene) wild-type and BRAF (v-raf murine sarcoma viral oncogene homolog B) wild-type, arising in the descending colon (left-sided). After starting therapy the patient develops an acneiform rash. Integrating biomarker selection, tumor sidedness, and the meaning of the rash, which statement is correct?
A) The left-sided location predicts poor benefit, so cetuximab should be stopped despite the wild-type RAS status
B) The acneiform rash indicates treatment failure and mandates immediate discontinuation
C) A RAS mutation would have enhanced benefit, so testing for one should be repeated before continuing
D) This patient is an appropriate cetuximab candidate: wild-type RAS and BRAF plus a left-sided primary predict benefit, and the acneiform rash is an expected on-target effect that correlates positively with response, managed with prophylactic oral tetracyclines rather than discontinuation
E) Tumor sidedness is irrelevant to anti-EGFR benefit, and the rash should be treated by permanently stopping the antibody
ANSWER: D
Rationale:
Anti-EGFR benefit requires wild-type RAS (and wild-type BRAF for single-agent activity), and left-sided primary tumors derive substantially more benefit than right-sided tumors. The acneiform rash is an on-target effect of EGFR blockade whose severity correlates positively with response and survival; it is managed with prophylactic oral tetracyclines such as doxycycline, not by stopping the drug. This patient meets all favorable criteria.
Option A: Option A is incorrect because left-sided location predicts better, not worse, benefit.
Option B: Option B is incorrect because the rash signals on-target activity, not failure.
Option C: Option C is incorrect because a RAS mutation predicts lack of benefit, not enhancement, and the tumor is already correctly wild-type.
Option E: Option E is incorrect because sidedness is relevant and the rash does not warrant permanent discontinuation.
5. A patient is scheduled to begin rituximab (an anti-CD20 [a B-cell surface antigen] antibody) for B-cell lymphoma. The team plans pre-treatment screening and vaccination. Integrating rituximab's infectious-risk and immunization implications, which combined plan is correct?
A) Screen for hepatitis B (surface antigen and core antibody) and provide antiviral prophylaxis if positive; administer needed inactivated vaccines (such as influenza and pneumococcal) before starting if feasible because B-cell depletion will blunt vaccine responses for months; and avoid all live vaccines because they are contraindicated during B-cell-depleting therapy
B) No hepatitis B screening is needed, but live vaccines should be given during therapy to maximize protection
C) Screen for hepatitis B but give live vaccines freely during therapy, since B-cell depletion does not affect vaccine safety
D) Defer all vaccines until after therapy and skip hepatitis B screening, since reactivation is not a concern with rituximab
E) Provide live vaccines before therapy and skip inactivated vaccines, since only live vaccines are effective in this setting
ANSWER: A
Rationale:
Three principles combine. Rituximab-mediated B-cell depletion can trigger hepatitis B reactivation, so screening for surface antigen and core antibody is mandatory, with antiviral prophylaxis for positives. B-cell depletion blunts responses to vaccines for 6 to 9 months, so needed inactivated vaccines should be given before therapy when feasible. Live vaccines are contraindicated in B-cell-depleted patients because the attenuated strain can cause disseminated infection.
Option B: Option B is incorrect because hepatitis B screening is mandatory and live vaccines are contraindicated.
Option C: Option C is incorrect because live vaccines are unsafe during B-cell depletion.
Option D: Option D is incorrect because hepatitis B reactivation is a serious concern and screening is required.
Option E: Option E is incorrect because live vaccines are contraindicated and inactivated vaccines are the appropriate pre-therapy immunizations.
6. Trastuzumab deruxtecan (T-DXd) is active in HER2-low (low-level HER2 [human epidermal growth factor receptor 2]-expressing) breast cancer and also carries a notable pulmonary toxicity. Integrating its drug-to-antibody ratio, payload properties, and the bystander effect, which statement correctly links the design features to both its efficacy in HER2-low disease and its characteristic toxicity?
A) Its low drug-to-antibody ratio and membrane-impermeant payload explain both its HER2-low activity and an absence of pulmonary toxicity
B) Its activity in HER2-low disease comes solely from the antibody's affinity, and its main toxicity is nephrotoxicity unrelated to the payload
C) A non-cleavable linker prevents any payload release, so neither bystander killing nor lung toxicity occurs
D) Its high drug-to-antibody ratio reduces potency, which is why it works only in strongly HER2-positive tumors
E) Its high drug-to-antibody ratio (approximately 8) and cleavable, membrane-permeable topoisomerase I inhibitor payload enable bystander killing that produces activity even at low HER2 expression, and that same permeable payload is implicated in interstitial lung disease, its most serious characteristic toxicity
ANSWER: E
Rationale:
T-DXd carries a high drug-to-antibody ratio (approximately 8) and a cleavable linker that releases a membrane-permeable topoisomerase I inhibitor. The released payload can diffuse into neighboring cells (bystander killing), producing activity even when HER2 expression is low, which underlies the HER2-low indication. The same membrane-permeable payload, through bystander effects on pulmonary epithelium combined with inflammatory mechanisms, is implicated in interstitial lung disease, the drug's most serious characteristic toxicity.
Option A: Option A is incorrect because T-DXd has a high ratio and a permeable payload, and it does carry pulmonary toxicity.
Option B: Option B is incorrect because activity arises from the high payload load and bystander killing, not affinity alone, and the main serious toxicity is pulmonary, not renal.
Option C: Option C is incorrect because T-DXd uses a cleavable, not non-cleavable, linker and does release payload.
Option D: Option D is incorrect because the high ratio increases delivered potency and extends activity into HER2-low disease.
7. A patient who completed daratumumab (an anti-CD38 [cyclic ADP-ribose hydrolase] antibody) for multiple myeloma two months ago now needs an urgent transfusion, and the antibody screen is pan-reactive. Integrating the mechanism, the duration of interference, and the recommended pre-treatment steps, which statement best guides safe transfusion?
A) The interference resolves within 48 hours of the last dose, so this two-month-old result must reflect a true new alloantibody
B) Daratumumab binds CD38 on red blood cells and produces a pan-reactive false-positive antibody screen that can persist up to about 6 months after the last dose; because baseline typing and antibody screening should have been recorded before the first dose and the blood bank notified, special techniques such as dithiothreitol-treated reagent cells (or least-incompatible units in an emergency) allow safe transfusion despite the interference
C) The patient's ABO type has been permanently altered by daratumumab, so emergency transfusion is impossible
D) The pan-reactive screen indicates active hemolysis and contraindicates any transfusion
E) Because daratumumab has been stopped, no special blood bank techniques are needed and routine crossmatch is fully reliable
ANSWER: B
Rationale:
Daratumumab binds CD38 on red blood cells and produces a pan-reactive false-positive antibody screen that can persist up to roughly 6 months after the last dose, so a result two months out is consistent with residual interference rather than a new alloantibody. Correct practice records baseline typing and screening before the first dose and notifies the blood bank; special techniques such as dithiothreitol treatment of reagent cells, or least-incompatible units in an emergency, then permit safe transfusion.
Option A: Option A is incorrect because the interference can last about 6 months, not 48 hours.
Option C: Option C is incorrect because daratumumab does not change the ABO type.
Option D: Option D is incorrect because the pan-reactivity is test interference, not evidence of hemolysis.
Option E: Option E is incorrect because the interference outlasts dosing, so special techniques remain necessary.
8. A patient with metastatic triple-negative breast cancer is starting sacituzumab govitecan, whose payload is SN-38 (the active metabolite of irinotecan). Pre-treatment genotyping returns UGT1A1*28/*28 (homozygous). Integrating the pharmacogenomic mechanism with the anticipated clinical course, which management approach is best?
A) No change is needed because UGT1A1 (uridine diphosphate-glucuronosyltransferase 1A1) genotype does not affect SN-38 handling
B) The homozygous genotype accelerates SN-38 clearance, so a higher-than-standard dose is required for efficacy
C) Because UGT1A1*28/*28 reduces UGT1A1 activity and impairs glucuronidation of SN-38, the patient is at higher risk of severe neutropenia and diarrhea; anticipate this by considering a lower starting dose and intensified toxicity monitoring with prompt management of myelosuppression and diarrhea
D) The genotype predicts hypersensitivity reactions specifically, so the main adjustment is added antihistamine pre-medication
E) The genotype mandates switching to an anti-EGFR antibody instead, since SN-38 cannot be used in any UGT1A1*28 carrier
ANSWER: C
Rationale:
SN-38 is detoxified by UGT1A1-mediated glucuronidation. The UGT1A1*28/*28 genotype reduces UGT1A1 activity, impairing SN-38 clearance and raising SN-38 exposure; this predicts severe neutropenia and diarrhea. The appropriate response is to anticipate the toxicity with a lower starting dose and intensified monitoring, treating myelosuppression and diarrhea promptly.
Option A: Option A is incorrect because the genotype clearly affects SN-38 elimination.
Option B: Option B is incorrect because the homozygous genotype slows, not accelerates, SN-38 clearance, so a higher dose would increase toxicity.
Option D: Option D is incorrect because the predicted risk is myelosuppression and diarrhea, not a hypersensitivity profile.
Option E: Option E is incorrect because the agent can still be used with dose adjustment and monitoring; switching to an unrelated anti-EGFR antibody is not indicated, and heterozygotes can generally receive standard dosing.
9. A lymphoma service uses brentuximab vedotin and polatuzumab vedotin (both delivering monomethyl auristatin E, a microtubule polymerization inhibitor) and also manages patients on trastuzumab deruxtecan (deruxtecan payload) and sacituzumab govitecan (SN-38 payload). A patient on one of the monomethyl auristatin E conjugates develops a new dose-limiting toxicity. Integrating payload class with expected toxicity, which prediction is correct?
A) The monomethyl auristatin E conjugates are most likely to cause dose-limiting peripheral neuropathy from axonal microtubule disruption; interstitial lung disease is instead the signature toxicity of the deruxtecan conjugate, and neutropenia with diarrhea is characteristic of the SN-38 conjugate
B) All four conjugates share interstitial lung disease as their dominant dose-limiting toxicity
C) The monomethyl auristatin E conjugates characteristically cause interstitial lung disease, while the deruxtecan conjugate causes peripheral neuropathy
D) The SN-38 conjugate is the one expected to cause peripheral neuropathy, while the monomethyl auristatin E conjugates cause neutropenia only
E) Payload class does not predict toxicity; all four agents cause identical, interchangeable adverse effects
ANSWER: A
Rationale:
Payload class predicts the signature toxicity. Monomethyl auristatin E, a microtubule inhibitor, disrupts axonal microtubule transport and characteristically causes dose-limiting peripheral neuropathy (brentuximab vedotin, polatuzumab vedotin). Deruxtecan, a topoisomerase I inhibitor, is associated with interstitial lung disease (trastuzumab deruxtecan). SN-38, also a topoisomerase I inhibitor, characteristically causes neutropenia and diarrhea (sacituzumab govitecan).
Option B: Option B is incorrect because the four agents do not share interstitial lung disease as a common dominant toxicity.
Option C: Option C is incorrect because it swaps the microtubule-inhibitor and deruxtecan toxicities.
Option D: Option D is incorrect because peripheral neuropathy belongs to the monomethyl auristatin E conjugates, not the SN-38 conjugate.
Option E: Option E is incorrect because payload class does predict distinct toxicities.
10. A patient with breast cancer bone metastases and significant renal impairment needs an antiresorptive agent to reduce skeletal-related events. The team selects denosumab (an anti-RANKL [receptor activator of nuclear factor kappa-B ligand] antibody) over a bisphosphonate and plans supportive care. Integrating the elimination rationale with the required prophylaxis, which combined plan is correct?
A) Denosumab is chosen because it is renally cleared and therefore safer than bisphosphonates in renal impairment; no calcium or dental measures are needed
B) Denosumab is chosen for renal safety, but because it strongly stimulates bone resorption, hypercalcemia is the main risk to prevent
C) A bisphosphonate is actually preferred here because denosumab is contraindicated in renal impairment
D) Denosumab is appropriate because it does not depend on renal elimination, unlike bisphosphonates; because its potent osteoclast suppression predisposes to hypocalcemia, calcium and vitamin D co-supplementation is mandatory and any pre-existing hypocalcemia must be corrected first; and because of osteonecrosis-of-the-jaw risk, a dental evaluation with completion of invasive dental work before starting is recommended
E) Denosumab requires no monitoring because it has no clinically important electrolyte or dental toxicities
ANSWER: D
Rationale:
Denosumab is a monoclonal antibody that does not depend on renal elimination, so it can be used when renal impairment limits bisphosphonates. Its potent suppression of osteoclast-mediated resorption predisposes to hypocalcemia, making calcium and vitamin D co-supplementation mandatory and requiring correction of pre-existing hypocalcemia before starting. Because of osteonecrosis-of-the-jaw risk, a dental evaluation with completion of invasive procedures beforehand is recommended.
Option A: Option A is incorrect because denosumab is not renally cleared, and calcium and dental measures are required.
Option B: Option B is incorrect because the metabolic risk is hypocalcemia, not hypercalcemia, and denosumab suppresses rather than stimulates resorption.
Option C: Option C is incorrect because denosumab is usable, indeed often preferred, in renal impairment.
Option E: Option E is incorrect because denosumab has clinically important hypocalcemia and jaw-osteonecrosis risks requiring monitoring.
11. A pharmacology learner is asked to rank the relative immunogenicity (tendency to provoke anti-drug antibodies) of four therapeutic antibodies using only their International Nonproprietary Name suffixes: a "-omab," a "-ximab," a "-zumab," and a "-umab." Integrating the suffix-to-source rule with its immunogenicity implication, which ranking from highest to lowest immunogenicity is correct?
B) -omab (murine) > -ximab (chimeric) > -zumab (humanized) > -umab (fully human), because greater non-human protein content increases the risk of anti-drug antibodies
The suffix encodes the antibody source, which correlates with immunogenicity: murine (-omab) is most immunogenic, chimeric (-ximab, roughly 25 to 35 percent human) is moderately immunogenic, humanized (-zumab, roughly 90 to 95 percent human) is less immunogenic, and fully human (-umab) is least immunogenic. The ordering tracks decreasing non-human protein content.
Option A: Option A is incorrect because it reverses the order, placing fully human as most immunogenic.
Option C: Option C is incorrect because humanized and fully human are not the most immunogenic; murine is.
Option D: Option D is incorrect because the source substem does encode species origin, which determines immunogenicity.
Option E: Option E is incorrect because chimeric is not more immunogenic than murine, and the overall ordering is scrambled.
12. A pharmacy receives an order that references "trastuzumab" for a patient whose chart indicates the intended agent is the antibody-drug conjugate trastuzumab emtansine (T-DM1). Integrating the medication-safety concern with the distinct toxicity profile of T-DM1, which statement is correct?
A) Trastuzumab and T-DM1 are interchangeable, so the shared prefix is sufficient to dispense either one
B) Substituting trastuzumab for T-DM1 carries no clinical consequence because they have identical mechanisms and toxicities
C) The two should be distinguished only for billing purposes; their pharmacology is the same
D) T-DM1 has no payload-specific toxicity, so the only issue is the drug name on the label
E) Trastuzumab and T-DM1 are distinct drugs that must never be substituted; T-DM1 carries a cytotoxic emtansine payload with characteristic thrombocytopenia and hepatotoxicity, so verification of the full drug name (not just the trastuzumab prefix) is mandatory to prevent harmful errors
ANSWER: E
Rationale:
Trastuzumab and trastuzumab emtansine (T-DM1) are distinct drugs with different mechanisms, dosing, indications, and toxicities, and confusion between them has caused fatal errors. T-DM1 carries a cytotoxic emtansine (DM1) payload and characteristically causes thrombocytopenia (through disruption of megakaryocyte microtubule dynamics) and hepatotoxicity. Verification of the full drug name, not just the shared trastuzumab prefix, is mandatory at every dispensing step.
Option A: Option A is incorrect because the agents are not interchangeable and the shared prefix is precisely the error trap.
Option B: Option B is incorrect because substitution has serious consequences given the distinct payload and toxicities.
Option C: Option C is incorrect because their pharmacology differs substantially, not just billing.
Option D: Option D is incorrect because T-DM1 has payload-specific toxicities such as thrombocytopenia and hepatotoxicity.
13. A clinician must counsel several patients of childbearing potential who are receiving therapeutic monoclonal antibodies and antibody-drug conjugates about pregnancy risk. Integrating the placental transfer mechanism with the implications for both antibody and conjugate classes, which statement is correct?
A) Monoclonal antibodies cannot cross the placenta, so pregnancy poses no risk and contraception is unnecessary
B) Only the cytotoxic payload of an antibody-drug conjugate poses fetal risk, while the antibody component is entirely safe in pregnancy
C) Because the neonatal Fc receptor actively transports immunoglobulin G across the placenta in the second and third trimesters, therapeutic antibodies reach the fetus and can affect fetal development; antibody-drug conjugates pose dual risk from both the transferred antibody and the cytotoxic payload, so effective contraception is required during therapy and for defined periods afterward
D) Placental antibody transfer occurs only in the first trimester, so therapy is safe once the second trimester begins
E) Fetal risk depends solely on renal excretion of the antibody, which is negligible, so no contraception is needed
ANSWER: C
Rationale:
The neonatal Fc receptor that recycles immunoglobulin G also mediates active transplacental transport of maternal antibody, predominantly in the second and third trimesters, so therapeutic antibodies reach the fetus and can disrupt fetal development. Antibody-drug conjugates pose dual risk because both the transferred antibody and the cytotoxic payload can cause fetal harm; effective contraception is required during therapy and for defined periods after the last dose.
Option A: Option A is incorrect because antibodies do cross the placenta via the neonatal Fc receptor.
Option B: Option B is incorrect because the antibody component also crosses and is not entirely safe; risk is dual for conjugates.
Option D: Option D is incorrect because transfer is greatest in the second and third trimesters, not confined to the first.
Option E: Option E is incorrect because fetal risk arises from placental transfer, not renal excretion, and contraception is required.
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