Bosutinib
Bosulif · BCR-ABL TKI
Reversible eGFR decline.
PSEUDOPRE
MildOpen →
CDK4/6 inhibitor
Palbociclib
Ibrance · Palbo
A CDK4/6 inhibitor that nudges creatinine up without truly injuring the kidney.
MildCDK4/6 inhibitor · approved 2015
HR-positive HER2-negative breast cancer
Signature kidney injury
Pseudo-AKI
A reversible rise in serum creatinine is common, but true structural kidney injury is uncommon. CDK4/6 inhibitors block the proximal-tubule transporters that secrete creatinine, producing a 'pseudo-AKI' picture. In a single-centre cohort, 17.5% of palbociclib-treated patients met creatinine-based AKI criteria, and when cystatin C was available, 73% of those events proved to be pseudo-AKI rather than a true GFR decline.
Source: Buijs et al., Br J Cancer 2025
Toxicity fingerprint
Tap a signature to trace where it strikes the nephron.
Incidence not quantified
SeverityMild
ReversibilityReversible
Evidence0 refs
Nephron map
Vasculature / Endothelium
Proximal TubuleBulk reabsorption + drug uptake (OCT2, OATs)
Distal Tubule / Collecting Duct
Pseudo-AKI
The great mimic — a rise in creatinine from blocked tubular secretion (OCT2/MATE), NOT true injury. The GFR is intact; confirm with cystatin C before stopping effective therapy.
Mechanism of kidney injury
Inhibits proximal-tubular organic cation transporter 2 (OCT2) and the MATE1/MATE2-K efflux transporters that secrete creatinine into the tubular lumen, elevating measured serum creatinine without reducing true glomerular filtration ('pseudo-AKI'). Cystatin C, which is filtered at the glomerulus and not secreted, is unaffected, so a cystatin-C-based eGFR unmasks the artefact. Genuine prerenal or structural injury, when present, is usually driven by intercurrent illness, volume depletion, or co-medications; rare true acute tubular injury and acute interstitial nephritis have been described.
Clinical presentation
Asymptomatic, early rise in serum creatinine (typically grade 1-2) with a stable or improved cystatin-C-based eGFR; urinalysis is bland with no proteinuria or active sediment. The discordance between rising creatinine and stable cystatin C is the diagnostic hallmark.
Onset
Often within the first 1-2 cycles (median onset roughly 30-35 days); creatinine plateaus and reverses after dose hold or discontinuation.
Reversibility
Reversible
Anticancer mechanism
Selectively inhibits cyclin-dependent kinases 4 and 6, blocking retinoblastoma protein (Rb) phosphorylation and arresting the cell cycle at the G1/S checkpoint. Combined with endocrine therapy for HR-positive, HER2-negative early-stage and advanced breast cancer.
Management
Distinguish pseudo-AKI from true AKI using a cystatin-C-based eGFR or the creatinine trend; a bland urinalysis and stable cystatin C support continuing therapy at full dose. Reserve dose reduction or interruption for genuine GFR decline. Treat real prerenal contributors (volume, drugs) conventionally; refer for biopsy only if proteinuria, active sediment, or unexplained progressive decline suggest AIN/ATN.
Risk factors
- Older age (>=65 years)
- Higher baseline creatinine/urea
- Volume depletion or concurrent nephrotoxins
- Concomitant CYP3A4 inhibitors raising drug exposure
Prevention
- Recognize transporter-mediated pseudo-AKI before stopping effective therapy
- Confirm with cystatin C or measured GFR when creatinine rises
- Maintain euvolemia; review concomitant nephrotoxins and CYP3A4 interactions
Note · Generally renally well tolerated; the dominant 'renal' signal is an artefactual creatinine rise from OCT2/MATE inhibition rather than true nephrotoxicity.
Clinical depth
Renal dose adjustment
No renal dose adjustment is specified for mild-to-moderate impairment; pharmacokinetic data in severe impairment/ESKD are limited. Do not dose-reduce for an isolated creatinine rise that is actually pseudo-AKI.
Dialyzability & ESKD dosing
Highly protein-bound, large volume of distribution, and hepatically (CYP3A4) metabolized; not meaningfully removed by hemodialysis. No HD-timed dosing established.
Differential diagnosis
Pseudo-AKI (stable cystatin C, bland urine) vs prerenal azotemia (volume signs, high BUN:Cr) vs true acute tubular injury or CDK4/6-associated AIN (proteinuria, pyuria, eosinophiluria, progressive decline). The single most useful test is a paired cystatin-C eGFR.
Monitoring
- Serum creatinine each cycle
- Cystatin-C-based eGFR when creatinine rises >=0.3 mg/dL or >25% from baseline
- CBC with differential (primary dose-limiting toxicity is neutropenia)
Key trials & series
- PALOMA-2/PALOMA-3 (registrational efficacy)
- Buijs Br J Cancer 2025 pseudo-AKI cohort
- Ly J Oncol Pharm Pract 2024 class-effect pseudo-Scr analysis
Clinical pearls
- A creatinine bump in the first two cycles with a normal cystatin C is pseudo-AKI - do not stop an effective drug.
- Up to ~12% of patients have had palbociclib unjustly dose-reduced or stopped for what was only transporter inhibition.
- The effect mirrors trimethoprim and cobicistat - secretion blockade, not injury.
Where it strikes
Nephron segments
Vasculature / Endothelium
Glomerular & peritubular capillaries
Proximal Tubule
Bulk reabsorption + drug uptake (OCT2, OATs)
Injury signatures
Pseudo-AKIPrerenal / Hemodynamic AKIElectrolyte Wasting
Evidence
6 peer-reviewed references. Citation metadata via PubMed / NLM.
LandmarkPseudo acute kidney injury in patients receiving CDK4/6 inhibitors.Buijs SM et al. · Br J Cancer 2025 · PMID 39930149Cohort using cystatin C to show 73% of creatinine rises on CDK4/6 inhibitors are pseudo-AKI from blocked tubular secretion.PMIDRenal adverse events associated with cyclin-dependent kinase 4/6 inhibitors.Izzedine H et al. · Cancer Treat Rev 2025 · PMID 41385991Dedicated onconephrology review of CDK4/6-inhibitor renal effects: OCT2/MATE pseudo-AKI, rare true ATN/AIN, hypertension, and electrolyte changes.PMIDEvaluation of cyclin-dependent kinase 4/6 inhibitor-induced serum creatinine elevations in patients with hormone receptor positive breast cancer.Ly E et al. · J Oncol Pharm Pract 2026 · PMID 39648753Shows pseudo-creatinine elevation is a class effect (palbociclib 16%, ribociclib 14%, abemaciclib 20%), nearly all grade 1-2.PMIDNephrotoxicity secondary to CDK 4/6 inhibitors in advanced breast cancer patients and its impact on survival.Avci T et al. · Ther Adv Med Oncol 2026 · PMID 41523909Retrospective cohort: ~23% had >=20% creatinine-clearance decline; older age and higher baseline urea/creatinine were risk factors.PMIDOnconephrology: The intersections between the kidney and cancer.Rosner MH et al. · CA Cancer J Clin 2020 · PMID 32853404Authoritative onconephrology review covering drug-induced renal effects and electrolyte disorders.PMIDOnconephrology: mitigation of renal injury in chemotherapy administration.Selamet U et al. · Curr Opin Nephrol Hypertens 2024 · PMID 38095483Reviews cell-cycle-inhibitor nephrotoxicity and strategies to mitigate chemotherapy-associated kidney injury.