ASCENT

Background

Phase III, open-label RCT. 529 patients with relapsed/refractory unresectable metastatic TNBC (brain metastasis cohort excluded from primary analysis) who had received ≥2 prior lines of chemotherapy for metastatic disease, including a taxane. Sacituzumab govitecan (SG) delivers SN-38 (active metabolite of irinotecan) via anti-Trop-2 antibody. Trop-2 is overexpressed in ~90% of TNBC.

Interventions and follow up

Arm A: Sacituzumab govitecan 10mg/kg IV days 1 and 8 of 21-day cycle
Arm B: Physician's choice single-agent chemotherapy (eribulin, vinorelbine, capecitabine, or gemcitabine)
Primary endpoint: Progression-free survival (PFS)
mFollow up: 17.7 month

Results

PFS: 5.6 vs 1.7mo, HR 0.41, 95% CI 0.32–0.52, P<.001
OS: 12.1 vs 6.7mo, HR 0.48, 95% CI 0.38–0.62, P<.001
ORR: 35% vs 5%

Adverse events

Hematologic: Grade ≥3 neutropenia 51.0% vs 33.0%; grade ≥3 anemia 8.0% vs 5.0%; febrile neutropenia 6.0% vs 2.0%
Gastrointestinal: Grade ≥3 diarrhea 10.0% vs 1.0%
Dermatologic: Alopecia 46.0%
Pharmacogenomic: UGT1A1*28 homozygous patients require dose reduction (higher SN-38 exposure)
Overall: Discontinuation 4.8% vs 5.4%

Conclusions

Sacituzumab govitecan significantly improved both PFS (HR 0.41) and OS (HR 0.48) vs chemotherapy in heavily pretreated metastatic TNBC — one of the largest hazard ratios for OS ever reported in this setting. ASCENT established SG as a new standard for relapsed/refractory mTNBC after prior taxane.

Key Limitations

Key Limitations: Brain metastasis patients (an important TNBC subgroup) were excluded from primary analysis. Grade ≥3 neutropenia in >50% of patients requires G-CSF support and careful monitoring. UGT1A1 genotyping should be considered to identify patients at high SN-38 toxicity risk. Trop-2 expression was not used for patient selection — Trop-2 IHC testing is not required per label, and the predictive value of Trop-2 expression for SG efficacy remains uncertain. Emerging head-to-head data vs T-DXd in TNBC are pending (DESTINY-Breast12 for non-TNBC; TNBC comparisons are evolving).

Clinical Context

ASCENT established sacituzumab govitecan (Trodelvy) as standard 2nd/3rd-line therapy in mTNBC (FDA regular approval 2021). ESMO-MCBS score: 5. SG is now being tested in earlier lines — ASCENT-04/KEYNOTE-D19 (SG + pembrolizumab vs standard 1st-line therapy in PD-L1+ mTNBC) showed positive PFS results (ASCO 2024). UGT1A1 testing is recommended but not required. Monitoring for ILD is prudent given topoisomerase I payload.

References

References: Bardia A et al, NEJM 2021