Biopharma March 2026 Oncology Sales: BTK and CDK4/6 Shifts Outpace IO Maturation; IQVIA Divergence Demands Caution

Core Conclusion

March 2026 IQVIA oncology sales reveal three structural trends: fragmentation of mature IO markets (steady 6–11% YoY), rapid share reallocation in BTK (Imbruvica -50% YoY, Brukinsa +39%, Calquence +23%), and acceleration in CDK4/6 switching (Kisqali +43% YoY). Concurrently, generic/biosimilar erosion is accelerating (Revlimid -66%, Zytiga -46%). Data reliability is deteriorating: IQVIA vs. actual reported sales divergences widened to -28% (Ibrance), -31% (Verzenio), -46% (Revlimid), and +83% (Rybrevant), requiring independent validation before portfolio decisions.

BTK Inhibitor Market: Share Consolidation Along Efficacy/CNS Profile

Imbruvica (AbbVie) annualized sales collapsed to $1.34B (-50% YoY), while Calquence (AZN, $3.51B, +23%) and Brukinsa (BeiGene, $3.01B, +39%) captured the growth. Brukinsa now holds 44% of oral BTK weekly TRx share, versus Imbruvica 31%, Calquence 20%, and Jaypirca 5%. In CLL specifically, Imbruvica still leads total TRx (36%) but declining; Brukinsa (16%) and Calquence (19%) are gaining rapidly. Jaypirca (Eli Lilly, annualized $619M, +68%) is growing but from a small base.

Evidence: Weekly TRx trends (through Apr 17) confirm acceleration: Brukinsa +37% vs. 12-wk rolling +33%; Calquence +24% vs. +20%; Imbruvica -4% vs. -15%. Brukinsa’s CLL approval (Jan 2023) drove sustained share gains. IQVIA accuracy for Imbruvica shows a -5% gap vs. actual in 1Q26, suggesting the reported -50% may be directionally correct but not precise.

Investment implication: BeiGene’s Brukinsa is the primary beneficiary, but its revenue concentration (~$3B on a likely modest overall revenue base) exposes it to competitive risk from future BTK degraders or combination therapies. AstraZeneca’s Calquence offers growth but faces margin pressure from ongoing IO/chemotherapy combo trials.

CDK4/6 Inhibitors: Kisqali’s Momentum Challenges Ibrance/Verzenio Duality

The CDK4/6 class annualized $11.59B (+18% YoY), but composition is shifting. Kisqali (Novartis) grew 43% YoY to $4.03B, Verzenio (Lilly) slowed to +11% ($4.29B), and Ibrance (Pfizer) only +5% ($3.27B). Weekly TRx shares (through Apr 17) are Ibrance 42%, Verzenio 33%, Kisqali franchise 24%.

Evidence: IQVIA vs. actual sales discrepancies are widening sharply. Ibrance IQVIA negative variance to actual was -28% in 1Q26 (vs. -21% in 1Q25). Verzenio’s variance jumped to -31% (from -4% in 1Q25). Verzenio’s prescription data capture changed in May 2020, artificially boosting past TRx comparisons. Kisqali’s IQVIA-to-actual is not flagged, suggesting better alignment.

Investment implication: Novartis’ Kisqali is the class winner on growth, but the regulatory catalyst (FDA label expansion into early breast cancer) is already priced in. Lilly’s Verzenio may be losing momentum due to tolerability concerns or market saturation. Pfizer’s Ibrance faces structural share erosion, with its CDK4/6 franchise becoming a drag. The widening IQVIA gaps complicate near-term revenue modeling for all three.

Generic / Biosimilar Erosion: Revlimid and Zytiga Confirm Peak Passing

Revlimid (BMS) annualized sales fell 66% YoY to $1.50B; IQVIA captures only $446M vs. actual $243M in 1Q26, a -46% divergence indicating channel data severely underestimates generic penetration. Zytiga (J&J) declined 46% to $21M annualized. In biosimilars, Avastin biosimilar Mvasi captured 48% share; Rituxan biosimilar Ruxience reached only 19% due to missing RA/PV label.

Evidence: The Revlimid IQVIA vs. actual chart shows the gap emerged sharply after generic entry (late 2022). The report explicitly warns “data skewed and not representative of actual figures due to manufacturer data blocks.” Biosimilar market share for Herceptin, Neulasta, Epogen is rising but not yet dominant (e.g., Herceptin Kanjinti only 8%). The PARP class (Lynparza stable +11% YoY, Zejula -23%, Talzenna +32%) is explicitly flagged as unreliable for IQVIA.

Investment implication: BMS faces ongoing Revlimid revenue headwinds not fully captured by IQVIA. J&J’s Zytiga legacy has minimal impact. For Gilead (Trodelvy +33% YoY, annualized $1.13B), biosimilar risk is minimal but future pipeline competition is the real threat.

Data Reliability Risk: IQVIA-Reported Divergence Demands Cross-Verification

Across multiple drug classes, the gap between IQVIA channel data and company-reported actuals widened materially in 1Q26. Ibrance (-28%), Verzenio (-31%), Revlimid (-46%), and Rybrevant (+83%) represent extreme cases. Elahere (AbbVie) shows IQVIA capturing essentially zero ($2M vs. $160M actual). PARP inhibitors are explicitly deemed “not useful” for IQVIA analysis.

Evidence: Historical accuracy for Keytruda, Tecentriq, Opdivo has been within single digits, indicating the problem is concentrated in older drugs with complex channel dynamics (discounts, REMS, specialty pharmacy shifts) and newer launches with limited prescription capture (Elahere via restricted distribution). The report normalizes sales for 5-week months (Mar/Jun/Sep/Dec = 25-35% inflation vs. 4-week), but even normalized data can mislead.

Investment implication: For hedge funds or active managers using IQVIA as a real-time read, these divergences create both opportunity (mispriced relative momentum) and risk (misjudging true commercial trajectory). The safest use case is directional trend analysis for drugs with high IQVIA-to-actual consistency (e.g., Keytruda, Verzenio prior to 1Q26), but Ibrance, Verzenio, and Revlimid now require explicit discounting.

Appendix: Key March 2026 Annualized IQVIA Sales Growth by Mechanism

Key Risks Beyond Data Quality: (1) Competitive launch of BTK degraders (e.g., NX-5948) could disrupt Brukinsa growth; (2) CDK4/6 label expansions (early breast) may have already peaked; (3) Biosimilar entry for Darzalex (expected 2028-29) not yet priced; (4) Medicare drug price negotiation (IRA) for Keytruda, Imbruvica, Ibrance may compress margins from 2027 onward.