Anticancer Drugs Practice Questions

Q: Vinca alkaloids act on:

Mitotic spindle. ### Explanation **Mechanism of Action (Why C is correct):** Vinca alkaloids (e.g., Vincristine, Vinblastine, Vinorelbine) are **cell-cycle specific** agents that act primarily during the **M phase** of the cell cycle. Their specific molecular target is **tubulin**. They bind to $\beta$-tubulin and **inhibit its polymerization** into microtubules. This prevents the formation of the **mitotic spindle**, leading to "mitotic arrest" in metaphase and subsequent apoptosis. **Analysis of Incorrect Options:** * **A & B (G and S phases):** Vinca alkaloids do not directly interfere with protein synthesis (G1/G2) or DNA replication (S phase). Antimetabolites like Methotrexate and 5-Fluorouracil are the classic drugs acting on the S phase. * **D (M phase):** While Vinca alkaloids act *during* the M phase, the question asks for the specific structure they act *on*. In pharmacology entrance exams, if both the phase (M phase) and the specific target (Mitotic spindle/Tubulin) are provided, the **molecular target** is the more precise and preferred answer. **High-Yield Clinical Pearls for NEET-PG:** * **Vincristine:** Notable for **Peripheral Neuropathy** (microtubules are essential for axonal transport) and **SIADH**. It is relatively bone marrow sparing. * **Vinblastine:** Notable for **Bone Marrow Suppression** ("Blast" blasts the bone marrow). * **Taxanes (Paclitaxel):** These also act on the mitotic spindle but have the *opposite* mechanism—they **prevent depolymerization** (stabilize microtubules), creating "frozen" spindles. * **Fatal Route:** Vinca alkaloids are **fatal if given intrathecally**; they must only be administered intravenously.

Q: Which of the following statements about Ifosfamide is INCORRECT?

It is less neurotoxic than cyclophosphamide.. ### Explanation **Why Option D is the correct (Incorrect) statement:** Ifosfamide is actually **more neurotoxic** than cyclophosphamide. This is because the metabolism of ifosfamide produces significantly higher levels of **chloroacetaldehyde**, a byproduct that crosses the blood-brain barrier and causes encephalopathy (confusion, seizures, or coma). In contrast, cyclophosphamide produces very little chloroacetaldehyde, making its neurotoxic profile much lower. **Analysis of other options:** * **Option A (Correct):** Ifosfamide is a structural isomer of cyclophosphamide and belongs to the **Nitrogen Mustard** class of alkylating agents. * **Option B (Correct):** It is a prodrug that requires hepatic activation. It is metabolized primarily by **CYP3A4** (and CYP2B6) to form the active alkylating species, **ifosfamide mustard**. * **Option C (Correct):** While ifosfamide mustard is the "active" cytotoxic metabolite for DNA cross-linking, **chloroacetaldehyde** is also a metabolite formed during the dechloroethylation pathway. It is clinically significant as it is responsible for the drug's characteristic neurotoxicity. **High-Yield Clinical Pearls for NEET-PG:** 1. **Hemorrhagic Cystitis:** Both ifosfamide and cyclophosphamide produce **Acrolein**, which causes bladder toxicity. However, the risk is higher with ifosfamide; therefore, **MESNA** (Mercaptoethane sulfonate) and aggressive hydration are mandatory. 2. **Fanconi Syndrome:** Ifosfamide is specifically associated with proximal renal tubular acidosis (Fanconi-like syndrome) due to chloroacetaldehyde-induced damage. 3. **Metabolism:** Unlike cyclophosphamide (primarily CYP2B6), ifosfamide relies heavily on **CYP3A4**, making it more prone to drug-drug interactions.

Q: A 30-year-old male diagnosed with Hodgkin's lymphoma was started on Bleomycin. Which of the following is false regarding Bleomycin?

It has a high risk of causing bone marrow suppression. Bleomycin is a unique glycopeptide antibiotic used in the treatment of Hodgkin’s lymphoma and testicular tumors. Its primary mechanism involves binding to DNA and iron, leading to the formation of free radicals that cause single- and double-strand DNA breaks [1]. **1. Why Option D is correct (The False Statement):** Bleomycin is famously known as a **"bone marrow-sparing"** drug. Unlike most cytotoxic agents, it causes minimal to no myelosuppression. This makes it a vital component of combination regimens like ABVD (Adriamycin, Bleomycin, Vinblastine, Dacarbazine), as it does not add to the hematological toxicity of other drugs. **2. Why other options are incorrect (True Statements):** * **Option A:** Pulmonary fibrosis is the most serious dose-limiting toxicity of Bleomycin [2]. It occurs because the lungs lack the inactivating enzyme (hydrolase), leading to oxidative damage. * **Option B:** Flagellate pigmentation (linear, whip-like hyperpigmented streaks on the trunk) is a pathognomonic cutaneous side effect of Bleomycin [2]. * **Option C:** Bleomycin is inactivated by the enzyme **Bleomycin hydrolase**. This enzyme is found in high concentrations in most tissues but is notably deficient in the **lungs and skin**, explaining why toxicity is localized to these organs. **High-Yield Clinical Pearls for NEET-PG:** * **Cell Cycle Specificity:** Bleomycin acts specifically on the **G2 phase** [1]. * **Monitoring:** Pulmonary Function Tests (PFTs), specifically **DLCO** (Diffusion Capacity of Carbon Monoxide), are used to monitor early lung toxicity. * **Maximum Cumulative Dose:** To prevent irreversible fibrosis, the lifetime dose is usually capped at **400 units**.

Q: Trastuzumab is directed against which of the following targets?

Human epidermal growth factor receptor 2. **Explanation:** **Trastuzumab** is a recombinant humanized monoclonal antibody specifically designed to target the **Human Epidermal Growth Factor Receptor 2 (HER2/neu)**, a proto-oncogene. In about 20–30% of breast cancer cases, HER2 is overexpressed, leading to uncontrolled cell proliferation. Trastuzumab binds to the extracellular domain of this receptor, inhibiting downstream signaling pathways (like MAPK and PI3K/Akt) and inducing antibody-dependent cellular cytotoxicity (ADCC). **Analysis of Options:** * **Option A (Correct):** Trastuzumab targets **HER2**. It is the first-line treatment for HER2-positive breast cancer and is also used in HER2-positive metastatic gastric adenocarcinoma. * **Option B (Incorrect):** **Bevacizumab** is the monoclonal antibody directed against Vascular Endothelial Growth Factor A (VEGF-A), used to inhibit angiogenesis. * **Option C (Incorrect):** Platelet-derived growth factor (PDGF) receptors are typically targeted by small molecule tyrosine kinase inhibitors like **Imatinib** or **Dasatinib**, rather than Trastuzumab. * **Option D (Incorrect):** FGF-23 is involved in phosphate metabolism. **Burosumab** is the monoclonal antibody that targets FGF-23, used in X-linked hypophosphatemia. **High-Yield Clinical Pearls for NEET-PG:** 1. **Cardiotoxicity:** The most significant side effect of Trastuzumab is **cardiac dysfunction** (decreased LVEF/heart failure). Unlike anthracyclines, this toxicity is usually **reversible** and not dose-dependent. 2. **Drug-Drug Interaction:** Never co-administer Trastuzumab with **Doxorubicin** due to a synergistic increase in the risk of heart failure. 3. **Resistance:** If resistance to Trastuzumab develops, **Lapatinib** (a dual EGFR/HER2 tyrosine kinase inhibitor) or **Ado-trastuzumab emtansine** (an antibody-drug conjugate) can be used.

Q: Ipilimumab is a:

CTLA4 inhibitor. **Ipilimumab** is a recombinant human monoclonal antibody that acts as an **immune checkpoint inhibitor**. Its primary mechanism involves binding to and blocking **CTLA-4** (Cytotoxic T-Lymphocyte Antigen 4), a molecule expressed on the surface of T-cells. Normally, CTLA-4 acts as an "off switch" to prevent overactivation of the immune system. By inhibiting this checkpoint, Ipilimumab allows T-cells to remain active and mount an effective immune response against tumor cells. It is primarily used in the treatment of advanced (metastatic) melanoma [1].**Analysis of Incorrect Options:** * **Option A (Anti-CD30):** This describes **Brentuximab vedotin**, which is used in Hodgkin lymphoma and Anaplastic large cell lymphoma [1]. * **Option B (PD-L1 inhibitor):** Drugs in this class include **Atezolizumab, Durvalumab, and Avelumab**. (Note: Nivolumab and Pembrolizumab are PD-1 inhibitors, not PD-L1). * **Option D (PTPN22 inhibitor):** PTPN22 is a gene associated with autoimmune diseases (like Rheumatoid Arthritis); there are currently no standard anticancer monoclonal antibodies targeting this in clinical practice.**High-Yield Clinical Pearls for NEET-PG:**1. **Mechanism:** Ipilimumab works at the **priming phase** (lymph node level), whereas PD-1 inhibitors work at the **effector phase** (tumor microenvironment).2. **Adverse Effects:** Checkpoint inhibitors cause **immune-related Adverse Events (irAEs)**, such as colitis, dermatitis, and hypophysitis (pituitary inflammation), and anti-CTLA-4 antibodies can be associated with autoimmune toxicity [1].3. **FDA Approval:** It was the first checkpoint inhibitor to show a survival benefit in metastatic melanoma.

Q: Methotrexate is used for the management of all of the following conditions except?

Sickle cell anemia. **Explanation:** **1. Why Sickle Cell Anemia is the Correct Answer:** Methotrexate (MTX) is a folate antagonist that inhibits the enzyme **dihydrofolate reductase (DHFR)**, leading to a decrease in DNA synthesis and cell proliferation [1]. It has no role in the management of Sickle Cell Anemia. The drug of choice for reducing the frequency of painful crises in Sickle Cell Anemia is **Hydroxyurea** [3], which acts by increasing the levels of Fetal Hemoglobin (HbF) [3]. **2. Analysis of Incorrect Options:** * **Rheumatoid Arthritis (RA):** MTX is the **"Anchor Drug"** and the first-line Disease-Modifying Anti-Rheumatic Drug (DMARD) for RA [2]. It acts by increasing adenosine levels, which exerts a potent anti-inflammatory effect. * **Psoriasis:** MTX is highly effective for severe, recalcitrant psoriasis and psoriatic arthritis due to its ability to inhibit the rapid proliferation of epidermal keratinocytes [2]. * **Organ Transplantation:** In low doses, MTX acts as an immunosuppressant used to prevent Graft-versus-Host Disease (GVHD) and organ rejection by inhibiting T-cell activation and proliferation [2]. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Competitive inhibition of DHFR; cell cycle-specific for the **S-phase** [1]. * **Toxicity:** Bone marrow suppression (most common), hepatotoxicity (cirrhosis), and pulmonary fibrosis [4]. * **Rescue Therapy:** **Leucovorin (Folinic acid)** is used to "rescue" normal cells from MTX toxicity by bypassing the inhibited DHFR enzyme [1], [4]. * **Contraindication:** It is highly **teratogenic** (causes neural tube defects and fetal death) [4]. * **Other Uses:** Choriocarcinoma (Drug of choice), Ectopic pregnancy, and Osteosarcoma.

Q: Which chemotherapeutic agent is most commonly administered by continuous infusion?

Cytarabine (Ara-C). **Explanation:** **Why Cytarabine (Ara-C) is the Correct Answer:** Cytarabine is a **cell-cycle specific (S-phase)** antimetabolite. Its mechanism involves inhibition of DNA polymerase. The primary reason for continuous infusion is its **extremely short half-life** (approximately 10–20 minutes) due to rapid deamination by the enzyme cytidine deaminase in the blood and liver. To maintain therapeutic plasma concentrations and ensure that leukemic cells entering the S-phase at different times are exposed to the drug, it is traditionally administered via continuous intravenous infusion (e.g., in the "7+3" regimen for AML). **Analysis of Incorrect Options:** * **5-Fluorouracil (5-FU):** While 5-FU is frequently given as a continuous infusion in colorectal cancer to improve the safety profile and efficacy, it is also commonly given as a bolus. In the context of standard pharmacological teaching for competitive exams, Cytarabine’s pharmacokinetics make it the classic prototype for continuous infusion. * **Cisplatin:** This is a cell-cycle non-specific alkylating-like agent. It is typically administered as a short-term infusion with aggressive pre- and post-hydration to prevent nephrotoxicity, rather than a continuous maintenance infusion. * **Etoposide:** An inhibitor of Topoisomerase II, usually administered as an intermittent intravenous infusion over 30–60 minutes to avoid hypotension. **NEET-PG High-Yield Pearls:** * **Drug of Choice:** Cytarabine is the backbone of Induction therapy for **Acute Myeloid Leukemia (AML)**. * **Specific Toxicity:** High-dose Cytarabine (HiDAC) is associated with **Cerebellar toxicity** (ataxia, nystagmus) and conjunctivitis (prophylactic steroid drops are used). * **Mechanism:** It is a pyrimidine analog (specifically a Cytidine analog).

Q: Paclitaxel acts on which phase of the cell cycle?

M. **Explanation:** **Mechanism of Action (Why M phase is correct):** Paclitaxel belongs to the **Taxane** class of anticancer drugs. Its primary mechanism is the **stabilization of microtubules** [2]. Unlike Vinca alkaloids (which prevent microtubule assembly), Paclitaxel binds to the $\beta$-tubulin subunit and promotes the assembly of microtubules while inhibiting their disassembly (depolymerization) [2]. This results in the formation of non-functional, stable microtubule bundles, leading to "mitotic freeze." Consequently, the cell cannot form a functional mitotic spindle, arresting the cell cycle specifically in the **M (Mitosis) phase** [3, 5]. **Analysis of Incorrect Options:** * **G1 Phase:** Drugs like Corticosteroids or L-asparaginase typically act here. Paclitaxel requires the presence of mitotic spindles, which are absent in G1. * **S Phase:** This is the site of action for Antimetabolites (e.g., Methotrexate, 5-FU) and DNA polymerase inhibitors (e.g., Cytarabine), which interfere with DNA synthesis [3]. * **G2 Phase:** Drugs like Bleomycin and Etoposide primarily exert their effects in the late S or G2 phase [3]. **NEET-PG Clinical Pearls:** * **Source:** Paclitaxel is derived from the bark of the Pacific Yew tree (*Taxus brevifolia*) [2]. * **Adverse Effects:** The dose-limiting toxicity is **Bone Marrow Suppression** (Neutropenia). It is also notorious for causing **peripheral neuropathy** [1] and **hypersensitivity reactions** (often due to the Cremophor EL vehicle; premedication with dexamethasone and antihistamines is required) [1]. * **Albumin-bound Paclitaxel (Abraxane):** A newer formulation that reduces hypersensitivity risks [1]. * **Mnemonic:** **T**axanes **T**erminate (stabilize) the **T**ubules.

Q: Methotrexate blocks the synthesis of thymidine monophosphate by inhibiting the activity of which enzyme?

Dihydrofolate reductase. ### **Explanation** **Correct Option: A. Dihydrofolate Reductase (DHFR)** Methotrexate (MTX) is a folate antimetabolite. It acts as a structural analog of folic acid and binds to the active site of **Dihydrofolate Reductase (DHFR)** with an affinity 1,000 times greater than the natural substrate. * **Mechanism:** By inhibiting DHFR, MTX prevents the conversion of dihydrofolate (DHF) to tetrahydrofolate (THF). * **Result:** THF is a crucial co-factor for the enzyme **Thymidylate Synthase**, which converts dUMP to dTMP (Thymidine monophosphate). Depletion of THF leads to a "thymineless death" of the cell, halting DNA synthesis and repair. **Analysis of Incorrect Options:** * **B. Orotate phosphoribosyl transferase:** This enzyme is involved in the **de novo synthesis of pyrimidines** (converting orotic acid to OMP). It is inhibited by 5-Fluorouracil (5-FU) metabolites, not Methotrexate. * **C. Ribonucleotide reductase:** This enzyme converts ribonucleotides to deoxyribonucleotides. It is the primary target of **Hydroxyurea**. * **D. Dihydroorotase:** This is an early-stage enzyme in pyrimidine biosynthesis. It is not a major target for common clinical antineoplastic agents. --- ### **High-Yield Clinical Pearls for NEET-PG** * **Leucovorin Rescue:** Folinic acid (Leucovorin) is given to "bypass" the blocked DHFR enzyme in normal cells during high-dose MTX therapy, preventing lethal hematological toxicity. * **Resistance Mechanism:** The most common cause of MTX resistance is the **amplification of the DHFR gene** or mutations in the DHFR enzyme. * **Polyglutamation:** Inside the cell, MTX undergoes polyglutamation, which traps the drug inside the cell and increases its inhibitory potency. * **Toxicity:** Watch for **Mucositis** (earliest sign), Nephrotoxicity (due to crystalluria), and Hepatotoxicity (cirrhosis with long-term use in Psoriasis/RA).

Q: Which of the following drugs is not categorized under anti-VEGF agents?

5-Fluorouracil. ### Explanation **Correct Answer: B. 5-Fluorouracil** **Why 5-Fluorouracil is the correct answer:** 5-Fluorouracil (5-FU) is an **Antimetabolite** (specifically a pyrimidine analog). Its primary mechanism of action is the inhibition of **thymidylate synthase**, which prevents the conversion of dUMP to dTMP. This leads to "thymineless death" of the cell by disrupting DNA synthesis. It does not directly target Vascular Endothelial Growth Factor (VEGF) or its receptors. **Analysis of Incorrect Options:** * **Bevacizumab:** A recombinant humanized **monoclonal antibody** that binds directly to circulating **VEGF-A** ligands, preventing them from binding to their receptors. It is widely used in colorectal and lung cancers. * **Ranibizumab:** A monoclonal antibody fragment (Fab) derived from bevacizumab. It is specifically designed for intravitreal injection to treat **neovascular (wet) Age-related Macular Degeneration (AMD)** by inhibiting VEGF. * **Sunitinib:** An oral **multi-targeted tyrosine kinase inhibitor (TKI)**. It inhibits the intracellular domain of **VEGFR-1, 2, and 3**, as well as PDGFR. It is a first-line agent for Renal Cell Carcinoma (RCC). **NEET-PG High-Yield Pearls:** 1. **VEGF Inhibitor Classification:** * **Antibodies (Ligand binders):** Bevacizumab, Ranibizumab, Aflibercept (VEGF Trap). * **Tyrosine Kinase Inhibitors (Receptor blockers):** Sunitinib, Sorafenib, Pazopanib. 2. **Side Effects of Anti-VEGFs:** Hypertension (most common), proteinuria, impaired wound healing, and arterial thrombosis. 3. **5-FU Toxicity:** Hand-foot syndrome (palmar-plantar erythrodysesthesia) and myelosuppression. Its action is enhanced by **Leucovorin** (folinic acid), which stabilizes the binding of 5-FU to thymidylate synthase.

Question 1

Vinca alkaloids act on:

Accepted Answer

Mitotic spindle

Answer

G phase

Answer

S phase

Answer

M phase

Question 2

Which of the following statements about Ifosfamide is INCORRECT?

Accepted Answer

It is less neurotoxic than cyclophosphamide.

Answer

It is a nitrogen mustard.

Answer

It is metabolized by CYP3A4 to form an active metabolite.

Answer

Chloracetaldehyde is an active metabolite.

Question 3

A 30-year-old male diagnosed with Hodgkin's lymphoma was started on Bleomycin. Which of the following is false regarding Bleomycin?

Accepted Answer

It has a high risk of causing bone marrow suppression

Answer

It can cause pulmonary fibrosis

Answer

It can cause flagellate pigmentation of skin

Answer

It is metabolized by hydrolase enzyme

Question 4

Trastuzumab is directed against which of the following targets?

Accepted Answer

Human epidermal growth factor receptor 2

Answer

Vascular endothelial growth factor A

Answer

Platelet derived growth factor

Answer

Fibroblast growth factor 23

Question 5

Ipilimumab is a:

Accepted Answer

CTLA4 inhibitor

Answer

Anti CD30 Monoclonal Antibody

Answer

PDL1 receptor inhibitor

Answer

PTPN22 inhibitor

Question 6

Methotrexate is used for the management of all of the following conditions except?

Accepted Answer

Sickle cell anemia

Answer

Rheumatoid arthritis

Answer

Psoriasis

Answer

Organ transplantation

Question 7

Which chemotherapeutic agent is most commonly administered by continuous infusion?

Accepted Answer

Cytarabine (Ara-C)

Answer

5-Fluorouracil (5-FU)

Answer

Cisplatin

Answer

Etoposide

Question 8

Paclitaxel acts on which phase of the cell cycle?

Accepted Answer

M

Answer

G1

Answer

S

Answer

G2

Question 9

Methotrexate blocks the synthesis of thymidine monophosphate by inhibiting the activity of which enzyme?

Accepted Answer

Dihydrofolate reductase

Answer

Orotate phosphoribosyl transferase

Answer

Ribonucleotide reductase

Answer

Dihydroorotase

Question 10

Which of the following drugs is not categorized under anti-VEGF agents?

Accepted Answer

5-Fluorouracil

Answer

Sunitinib

Answer

Ranibizumab

Answer

Bevacizumab

Anticancer Drugs — MCQs

Anticancer Drugs — MCQs

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