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HER2 TKI

Tucatinib

Tukysa · TUCA

HER2 TKI · approved 2020 · 4 references

The textbook 'pseudo-AKI' drug: a creatinine bump from blocked tubular secretion, not real kidney injury.

Signature injury
Pseudo-AKI
Severity
Mild
Reversibility
Reversible
Onset
Within the first weeks of therapy; plateaus and is fully reversible within days of discontinuation.

Signature kidney injury & incidence

Pseudo-AKI.

A mild creatinine increase is common and expected, but it reflects inhibition of tubular creatinine secretion (a 'pseudo-AKI' artifact) rather than true GFR loss. Dedicated transporter/PK studies show tucatinib inhibits renal OCT2 and MATE1/MATE2-K without changing iohexol-measured GFR.

Source: Topletz-Erickson et al., J Clin Pharmacol 2020

Reported injury signatures: Pseudo-AKI.

Onset timing & rechallenge

Subacute (~1–6 weeks) — Creatinine rises within the first weeks of therapy, then plateaus and fully reverses within days of stopping.

Mechanism of kidney injury

Tucatinib inhibits the renal organic cation transporter OCT2 (basolateral uptake) and MATE1/MATE2-K (apical efflux), which together secrete creatinine from blood into the proximal-tubule lumen. Creatinine is filtered AND secreted; blocking the secretory component raises serum creatinine while filtration (true GFR) is unchanged. This is an artifactual ('pseudo-AKI') rise — confirmed because iohexol-measured GFR is preserved.

Clinical presentation

Modest, early, stable creatinine elevation (often plateaus quickly) with completely bland urinalysis, no electrolyte derangement, no proteinuria, and preserved true GFR (cystatin C / measured GFR unchanged).

Management

Recognize as pseudo-AKI: do not discontinue tucatinib for an isolated stable creatinine rise with bland sediment. Confirm with cystatin C/measured GFR if needed. No specific renal treatment required. The creatinine artifact can also confound capecitabine dose decisions that rely on Cockcroft-Gault.

Risk factors

  • Baseline CKD (makes the creatinine shift more conspicuous)
  • Concurrent drugs that also inhibit creatinine secretion (e.g., trimethoprim, cimetidine, dolutegravir, cobicistat)

Prevention

  • Anticipate the benign creatinine rise and avoid unnecessary therapy interruption
  • Use cystatin C or measured GFR to confirm preserved true function before stopping effective therapy

Renal dose adjustment

No renal dose adjustment for mild-moderate impairment. The creatinine rise is NOT a reason to reduce tucatinib; but it can falsely lower estimated CrCl and inappropriately trigger capecitabine dose reduction — use cystatin C-based GFR or measured GFR for companion-drug dosing decisions. Limited data in severe impairment, and the label does not recommend the tucatinib + capecitabine + trastuzumab combination at CrCl <30 mL/min — a restriction it attributes to the capecitabine component.

Dialyzability & ESKD dosing

Not characterized; highly protein-bound, hepatically (CYP2C8/3A) cleared small molecule, unlikely to be appreciably dialyzed. No ESKD dosing data.

Differential diagnosis

Pseudo-AKI vs true AKI: a discordant creatinine-up / cystatin C-stable pattern is the signature.

Monitoring

  • Serum creatinine with a low threshold to add cystatin C if a rise prompts concern
  • Urinalysis (expected bland) to confirm absence of true injury
  • LFTs per label (hepatotoxicity is the more clinically relevant toxicity)

Key trials & series

  • Topletz-Erickson, J Clin Pharmacol 2020 — dedicated renal-transporter/GFR study establishing pseudo-AKI
  • HER2CLIMB — registrational efficacy trial (clinical context)

Clinical pearls

  • Cystatin C is the tie-breaker: creatinine up but cystatin C/measured GFR normal = pseudo-AKI, keep treating.
  • The artifact can sabotage Cockcroft-Gault-based capecitabine dosing — don't dose-reduce the partner drug off a falsely low CrCl.
  • This is the best-characterized OCT2/MATE creatinine-secretion artifact in oncology — the canonical teaching example.

Anticancer mechanism

Oral, highly HER2-selective tyrosine kinase inhibitor (minimal EGFR activity). Approved with trastuzumab and capecitabine for advanced HER2-positive breast cancer including brain metastases, and with trastuzumab for HER2-positive RAS-wild-type colorectal cancer.

Note

Clinician-flagged as a classic pseudo-AKI / creatinine-secretion artifact. Dedicated transporter PK data support the mechanism.

Guidelines & consensus

Each recommendation below is this atlas's faithful summary of the source, not a quotation from it — follow the PubMed link for the wording the society published. Summaries may be superseded; consult the current full text and individualize to the patient.

  • ADQI (2026) — The nephrotoxic effects of anti-cancer therapies: consensus report of the 34th Acute Disease Quality Initiative workgroupProvides expert-based statements (modified Delphi) on preventing and managing cisplatin/platinum-associated AKI, including isotonic IV hydration, attention to volume status and concomitant nephrotoxins, and incorporates evidence that IV magnesium supplementation may reduce cisplatin-associated AKI; emphasizes risk stratification and standardized AKI definitions.Nat Rev Nephrol · PMID 41361704
  • SIRM (2022) — SIRM-SIN-AIOM: appropriateness criteria for evaluation and prevention of renal damage in the patient undergoing contrast medium examinations-consensus statements from Italian College of Radiology (SIRM), Italian College of Nephrology (SIN) and Italian Association of Medical Oncology (AIOM)Recommends eGFR-based renal risk assessment and pre/post-contrast isotonic saline or sodium bicarbonate hydration; advises maintaining a 5-7 day interval between iodinated contrast administration and cisplatin in cancer patients to reduce additive nephrotoxicity.Radiol Med · PMID 35303246
  • KDIGO (2020) — KDIGO Controversies Conference on onco-nephrology: understanding kidney impairment and solid-organ malignancies, and managing kidney cancerIdentifies platinum compounds (especially cisplatin) as leading cytotoxic causes of acute tubular injury, AKI, and electrolyte/magnesium wasting; calls for interdisciplinary onco-nephrology care, accurate GFR estimation, and individualized drug dosing in patients with reduced kidney function.Kidney Int · PMID 33126977
  • KDIGO (2020) — KDIGO Controversies Conference on onco-nephrology: kidney disease in hematological malignancies and the burden of cancer after kidney transplantationAddresses chemotherapy-associated AKI/CKD in hematologic cancer, GFR estimation and chemotherapy dosing in patients with reduced kidney function, and management priorities and research gaps for onco-nephrology care.Kidney Int · PMID 33276867
  • ADDIKD (2025) — Integrating International Consensus Guidelines for Anticancer Drug Dosing in Kidney Dysfunction (ADDIKD) into everyday practiceProvides GRADE-based, drug-specific dose-adjustment recommendations for anticancer agents in kidney dysfunction (illustrated for methotrexate, cisplatin, carboplatin and nivolumab); the recommendations build on Part 1's standardised CKD-EPI eGFR assessment rather than Cockcroft-Gault creatinine clearance.EClinicalMedicine · PMID 40290844
  • ADDIKD (2025) — Aligning kidney function assessment in patients with cancer to global practices in internal medicineThree consensus recommendations: assess kidney function by GFR (measured GFR or CKD-EPI eGFR), classify it using KDIGO categories, and use this uniform approach to dose anticancer drugs — moving cancer medicine away from Cockcroft-Gault estimated creatinine clearance.EClinicalMedicine · PMID 40290845
  • ADDIKD (2025) — A methodology for determining dosing recommendations for anticancer drugs in patients with reduced kidney functionEstablishes that, where RCT evidence is lacking, anticancer drug dosing recommendations in kidney dysfunction should be derived by critically appraising observational literature via GRADE combined with structured international multidisciplinary consensus voting.EClinicalMedicine · PMID 40290846
  • KDIGO (2013) — Diagnosis, evaluation, and management of acute kidney injury: a KDIGO summary (Part 1)Defines/stages AKI by serum creatinine and urine output; emphasizes avoiding nephrotoxins, maintaining euvolemia/perfusion, dose-adjusting drugs to kidney function, and monitoring high-risk patients — the framework applied to nephrotoxic anti-cancer agents.Crit Care · PMID 23394211
  • KDIGO (2024) — Executive summary of the KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease: known knowns and known unknownsEvaluate and risk-stratify CKD, manage to delay progression and its complications, and practise explicit medication management and drug stewardship — the framework the atlas's G1–G5 eGFR banding and every renal dose-adjustment recommendation sit inside. Because the guideline excludes dialysis and transplant recipients by its own statement of scope, its recommendations do not carry to those settings, where this atlas's dialyzability and post-transplant guidance rests on other sources.Kidney Int · PMID 38519239
  • KDIGO (2021) — Executive summary of the KDIGO 2021 Guideline for the Management of Glomerular DiseasesProvides the staging/treatment framework for drug-associated glomerular lesions (e.g., bisphosphonate- and interferon-related collapsing FSGS, VEGF-inhibitor podocytopathy/proteinuria), including immunosuppression and supportive RAAS-blockade strategies.Kidney Int · PMID 34556300
  • KDIGO (2024) — Executive summary of the KDIGO 2024 Clinical Practice Guideline for the Management of ANCA-Associated VasculitisUpdates immunosuppressive induction (rituximab/cyclophosphamide), incorporates avacopan and lower-dose or glucocorticoid-sparing regimens — the management framework for drug- and checkpoint-inhibitor-associated ANCA/pauci-immune glomerulonephritis.Kidney Int · PMID 38388147
  • KDIGO (2024) — Executive summary of the KDIGO 2024 Clinical Practice Guideline for the Management of Lupus NephritisUpdates first-line lupus nephritis therapy to combination immunosuppression with the addition of belimumab or a calcineurin inhibitor (voclosporin) — informs management of immune-complex/lupus-like glomerulonephritis encountered with immunotherapy.Kidney Int · PMID 38182299
  • KDIGO (2025) — Executive summary of the KDIGO 2025 Clinical Practice Guideline for the Management of Immunoglobulin A Nephropathy (IgAN) and Immunoglobulin A Vasculitis (IgAV)Encourages liberal kidney biopsy and stricter proteinuria control (<0.5 g/d, ideally <0.3 g/d) with RAAS blockers, SGLT2 inhibitors, and targeted-release budesonide — the framework for IgA-dominant glomerular lesions, including those triggered by immune-modulating cancer therapy.Kidney Int · PMID 40975525

References

4 peer-reviewed references. Citation metadata via PubMed / NLM.

  1. 1.Tucatinib Inhibits Renal Transporters OCT2 and MATE Without Impacting Renal Function in Healthy Subjects.Topletz-Erickson AR et al. · J Clin Pharmacol · 2020 · PMID 32989831
  2. 2.Quantitative Consideration of Clinical Increases in Serum Creatinine Caused by Renal Transporter Inhibition.Nakada T et al. · Drug Metab Dispos · 2023 · PMID 36859345
  3. 3.Inhibitory effect of flavonoids on multidrug and toxin extrusion protein 1 function: Implications for food/herb-drug interaction and drug-induced kidney injury.Duan X et al. · J Appl Toxicol · 2024 · PMID 38760888
  4. 4.New drug toxicities in the onco-nephrology world.Perazella MA et al. · Kidney Int · 2015 · PMID 25671763
Educational monograph from NephTox (nephtox.com). Not medical advice — verify against current guidelines before any clinical decision.