The Targeted Pulse: Updates in Breast, Lung, and Lymphoma

Welcome to this week's edition of The Targeted Pulse, your weekly wrap-up of the top developments in oncology. This week, we saw several breakthroughs in targeted therapies, specifically in breast cancer treatment. From regulatory designations for promising new drugs to crucial clinical trials, here are the top stories that shaped the week.

Tazemetostat Withdrawn From All Trials and Markets Due to Safety Concerns

In a significant regulatory shift, the EZH2 inhibitor tazemetostat (Tazverik) has been voluntarily withdrawn from all global markets and ongoing clinical trials following emerging safety signals. The decision stems from an increased incidence of secondary malignancies, specifically T-cell lymphoblastic lymphoma, observed in both pediatric and adult cohorts.

For clinicians, this necessitates an immediate cessation of treatment for patients currently receiving the agent for epithelioid sarcoma or follicular lymphoma. Patients previously exposed to tazemetostat should be transitioned to alternative therapies and monitored long-term for hematologic irregularities. This withdrawal underscores the critical need for continued vigilance regarding epigenetic modifiers and their potential for off-target genomic instability.

Phase 3 Trial of Giredestrant Misses Primary PFS End Point

The phase 3 persevERA trial evaluating the oral selective estrogen receptor degrader (SERD) giredestrant in combination with palbociclib (Ibrance) failed to meet its primary end point of improved progression-free survival (PFS) in the first-line HR+/HER2- metastatic setting. While giredestrant showed a numerical PFS trend over letrozole plus palbociclib, it did not reach statistical significance in the intent-to-treat population.

Despite this frontline setback, giredestrant maintains clinical momentum through the positive evERA trial (second-line with everolimus) and the lidERA trial (adjuvant setting), both demonstrating significant benefit. Clinicians should monitor the forthcoming pionERA results (2027) for further clarity on sequencing next-generation SERDs after CDK4/6 progression.

Navigating Complexity: Key Updates to ASCO's Living Guidelines for Stage IV Driver Mutation–Negative NSCLC

The 2026 update to ASCO’s Living Guidelines for stage IV driver mutation-negative non-small cell lung cancer emphasizes a "test first, treat second" paradigm. Central to this update is the structural prioritization of comprehensive molecular testing to definitively exclude actionable drivers before initiating immunotherapy, mitigating toxicity risks associated with subsequent treatment switches.

Key therapeutic additions include the MET-targeted antibody-drug conjugate telisotuzumab vedotin (Teliso-V; Emrelis) for high MET-overexpressing tumors in subsequent lines. The guidelines maintain a complex framework stratified by histology and 3 PD-L1 expression tiers (≥50%, 1-49%, <1%), resulting in 6 distinct patient subsets. Clinicians are encouraged to utilize shared decision-making, particularly in PD-L1-negative squamous populations where no single regimen is superior, while awaiting definitive data from trials like INSIGNA and NIPPON on optimal chemo-free or dual checkpoint blockade strategies.

Sequencing Therapy for HER2-Positive Metastatic Breast Cancer: Emerging Strategies

This article outlines the shifting therapeutic paradigm for HER2-positive metastatic breast cancer, emphasizing the integration of novel antibody-drug conjugates (ADCs) and tyrosine kinase inhibitors (TKIs).

The standard first-line regimen remains a taxane plus trastuzumab (Herceptin) and pertuzumab (Perjeta), established by the CLEOPATRA trial. However, the second-line setting has shifted significantly: fam-trastuzumab deruxtecan-nxki (T-DXd; Enhertu) is now the preferred choice over ado-trastuzumab emtansine (T-DM1) based on superior PFS in the DESTINY-Breast03 trial. For patients with active brain metastases, the tucatinib (Tukysa)/capecitabine/trastuzumab triplet (HER2CLIMB) provides a critical evidence-based alternative.

Clinicians must navigate emerging "ADC-after-ADC" sequencing challenges, addressing potential cross-resistance from shared topoisomerase I payloads while monitoring for specific toxicities, such as interstitial lung disease. Ongoing trials like DESTINY-Breast05 and HER2CLIMB-05 continue to push these potent therapies into earlier treatment lines and maintenance settings.

Sequencing and Treatment Approaches for ADCs in HR+ Metastatic Breast Cancer

The treatment landscape for HR+/HER2-low metastatic breast cancer is evolving with the sequential use of ADCs. Following CDK4/6 inhibitor progression, T-DXd and sacituzumab govitecan-hziy (Trodelvy) are primary options. Clinical decision-making focuses on the "ADC after ADC" strategy, though cross-resistance—driven by shared topoisomerase I inhibitor payloads—remains a concern.

While the DESTINY-Breast04 and TROPHY-U-01 trials established efficacy, emerging data from the DESTINY-Breast06 trial suggest T-DXd may move into earlier lines. Clinicians must prioritize toxicity management, specifically interstitial lung disease (T-DXd) and neutropenia or diarrhea, while awaiting definitive sequencing data to optimize longitudinal patient outcomes.