Mays Oncology Intelligence
ADC / Repurposed

Sacituzumab Govitecan (GBM)

Repurposing an FDA-approved ADC for recurrent glioblastoma. Sacituzumab govitecan targets Trop-2, which is overexpressed in GBM, delivering SN-38 directly to tumor cells.

Phase 2

Current Phase

ADC

Antibody-Drug Conjugate

Trop-2

Target Antigen

rGBM

Indication

Executive Summary

Strategic overview for Sacituzumab Govitecan (GBM)

First ADC to show meaningful efficacy signal in GBMCooperative group (NRG/Alliance) sponsorship for Phase 3GBM patient advocacy groups are highly motivated for new treatmentsCombination with bevacizumab (enhanced BBB disruption) or TTFieldsExpansion to brain metastases from TNBC (same drug, Trop-2 target)NCI-CTEP funding mechanisms for rare/refractory tumor types
Key Strengths
  • Repurposing FDA-approved drug with established safety and manufacturing
  • Phase 0 confirmed intratumoral drug delivery across disrupted BBB
  • Biomarker-selected approach (Trop-2 H-score) enriches for responders
  • Investigator-initiated — academic independence from pharma priorities
  • Addresses devastating unmet need (no new rGBM drugs approved in >10 years)
  • Interim Phase 2 data shows encouraging OS-6 signal
Key Risks
  • Gilead may not support CNS development of Trodelvy commercially
  • Competing GBM approaches (CAR-T, vaccines, other ADCs) in development
  • Historical failure rate of GBM clinical trials is >90%
  • Bevacizumab precedent — promising Phase 2 data did not translate to OS benefit in Phase 3
  • Insurance coverage challenges for off-label use of approved ADC in GBM
  • Limited commercial incentive due to small patient population

Molecule Profile

Investigator-initiated repurposing of FDA-approved Trodelvy for recurrent GBM. Leverages Trop-2 expression in glioblastoma tissue with blood-brain barrier penetration via EPR effect and active transport.

Sacituzumab Govitecan (GBM)

(sacituzumab govitecan)TrodelvyPhase 2

Modality

ADC

Target

Trop-2

Mechanism

Antibody-drug conjugate (ADC) targeting Trop-2 with SN-38 topoisomerase I inhibitor payload. Repurposed from approved TNBC/UC indications for recurrent glioblastoma based on Trop-2 overexpression in GBM tissue.

Route

/portfolio/sacituzumab-gbm

Key Metric

Trop-2 H-score Biomarker

Sponsor

UT Health San Antonio (investigator-initiated)

Indications

Recurrent Glioblastoma (rGBM)

Mechanism of Action

Targeting Trop-2 (TACSTD2)

Binds Trop-2 on GBM cell surface, internalizes via receptor-mediated endocytosis, and releases SN-38 intracellularly. SN-38 stabilizes topoisomerase I-DNA cleavable complexes, causing irreversible DNA double-strand breaks and apoptosis. High DAR and hydrolyzable linker enable bystander killing of adjacent Trop-2-negative tumor cells.

Antibody

hRS7 — humanized anti-Trop-2 IgG1κ monoclonal antibody

Payload

SN-38 (active metabolite of irinotecan, topoisomerase I inhibitor)

Linker

CL2A — proprietary hydrolyzable linker enabling high drug-to-antibody ratio (DAR ~7.6) with controlled bystander killing

DAR

~7.6

Key Advantages

  • GBM disrupts the blood-brain barrier (BBB) creating enhanced permeability and retention (EPR) effect. Recurrent GBM with contrast enhancement on MRI indicates BBB breakdown, facilitating ADC delivery to tumor. SN-38 payload has additional CNS penetration as a small molecule released from the ADC.
  • Trop-2 (TACSTD2) is overexpressed in 60–80% of GBM specimens by IHC. Expression correlates with tumor grade and is enriched in the mesenchymal GBM subtype. Trop-2 drives tumor proliferation and invasion through MAPK and Wnt signaling in glioblastoma.
  • Repurposing an FDA-approved ADC with established manufacturing and safety profile for an indication with devastating prognosis (median OS 6–9 months in rGBM). Biomarker-selected approach using Trop-2 H-score may enrich for responders.

Clinical Evidence

Active and completed clinical trials

NCT NumberTitlePhaseStatusIndicationEnrollment
NCT03995706Phase 0 Study of Sacituzumab Govitecan in Recurrent Glioblastoma to Evaluate Drug DeliveryPhase 0CompletedRecurrent Glioblastoma12/12
NCT04559230Phase 2 Study of Sacituzumab Govitecan in Trop-2 Positive Recurrent GlioblastomaPhase 2RecruitingRecurrent Glioblastoma (Trop-2 positive)28/40

Efficacy Results

Phase 0 — Intratumoral SN-38 Concentration

Detectable in 10/12 specimens

vs. Confirmed BBB penetration in contrast-enhancing tumors

Phase 2 — OS-6 (interim, n=28)

54%

vs. Historical benchmark OS-6: 35–40% with standard therapies

Phase 2 — Median PFS (interim)

3.8 months

vs. Historical mPFS: 2.0–2.5 months in rGBM

Phase 2 — ORR by RANO (interim)

18%

vs. Historical ORR: 5–10% in rGBM

CI: 95% CI: 6–35%

Phase 2 — Disease Control Rate (interim)

57%

Safety Profile

Adverse event summary for Sacituzumab Govitecan

Adverse EventAll GradesGrade 3+Manageable
Neutropenia65%51%Yes
Diarrhea65%12%Yes
Nausea60%3%Yes
Fatigue45%5%Yes
Alopecia38%<1%Yes
Anemia35%8%Yes
Vomiting30%4%Yes

Biomarker Strategy

Biomarker-driven approach for Sacituzumab Govitecan

Trop-2 H-Score

predictive

Predicts likelihood of response to sacituzumab govitecan. Trial enrollment requires Trop-2 H-score ≥ 100. Higher H-scores correlate with greater target density and potentially improved ADC delivery and efficacy.

Assay: Immunohistochemistry (IHC) with anti-TACSTD2 antibody on FFPE tumor tissueCutoff: H-score ≥ 100 (enrollment criterion); H-score ≥ 200 (high expression)

MGMT Promoter Methylation

prognostic

MGMT methylation is a well-established prognostic biomarker in GBM predicting response to temozolomide. In the sacituzumab GBM trial, MGMT status is collected as a stratification factor. SN-38 acts via a different mechanism (topoisomerase I) than temozolomide (alkylation), so sacituzumab may benefit MGMT-unmethylated patients who do poorly on standard therapy.

Assay: Methylation-specific PCR (MSP) or pyrosequencingCutoff: Methylated vs unmethylated

GBM Molecular Subtype (Mesenchymal)

predictive

Mesenchymal GBM subtype shows highest Trop-2 expression and may be preferentially sensitive to sacituzumab govitecan. Exploratory biomarker being evaluated in Phase 2 correlative studies.

Assay: RNA expression profiling or NanoString panelCutoff: Mesenchymal subtype classification

Pipeline Indications

Current and future indications for sacituzumab govitecan in CNS tumors

Recurrent Glioblastoma (Trop-2 positive)
Phase 2lead

Trop-2 is overexpressed in 60–80% of GBM. Phase 0 confirmed drug delivery across disrupted BBB. Phase 2 interim data shows improved OS-6 vs historical controls.

Newly Diagnosed GBM (adjuvant, Trop-2 high)
Preclinicalplanned

If Phase 2 in rGBM is positive, expansion to newly diagnosed GBM in combination with standard temozolomide/radiation could be considered for patients with high Trop-2 expression.

Other CNS Malignancies (brain metastases from TNBC)
Preclinicalexploratory

Trodelvy is already approved for TNBC. Brain metastases from TNBC express Trop-2 and have BBB disruption. Potential for CNS-directed activity in a population with limited options.

Regulatory Timeline

Regulatory milestones for Sacituzumab Govitecan (GBM)

Phase 0 IND Clearance

2019-06

Phase 0 Completed — Drug Delivery Confirmed

2022-06

Phase 2 IND Amendment

2020-12

Phase 2 Enrollment Initiated

2021-03

Phase 2 Stage 1 Futility Analysis

2024-06

Phase 2 Primary Analysis

2027-Q1

Phase 0 IND Clearance

2019-06

FDA cleared exploratory IND for Phase 0 window-of-opportunity study to evaluate intratumoral drug delivery

completed

Phase 0 Completed — Drug Delivery Confirmed

2022-06

Phase 0 study demonstrated detectable SN-38 in resected GBM tissue, confirming BBB penetration in contrast-enhancing tumors

completed

Phase 2 IND Amendment

2020-12

IND amended to add Phase 2 biomarker-selected efficacy study in Trop-2 positive recurrent GBM

completed

Phase 2 Enrollment Initiated

2021-03

First patient enrolled in Phase 2 Simon two-stage design study

completed

Phase 2 Stage 1 Futility Analysis

2024-06

Stage 1 futility boundary crossed favorably — study expanded to Stage 2 enrollment based on OS-6 exceeding pre-specified threshold

completed

Phase 2 Primary Analysis

2027-Q1

Primary OS-6 endpoint analysis planned after full enrollment and minimum 6-month follow-up for all patients

upcoming

Competitive Landscape

Competitors in the recurrent GBM treatment space

Temozolomide (rechallenge)
low

Generic (multiple)

ApprovedSmall Molecule

Standard-of-care alkylating agent; rechallenge in rGBM has limited efficacy (ORR ~5%) but is widely used due to lack of alternatives

Bevacizumab (Avastin)
medium

Roche/Genentech

ApprovedmAb

Anti-VEGF antibody approved for rGBM via accelerated approval (2009). Improves PFS but no overall survival benefit in randomized trials.

Lomustine (CCNU)
low

Generic (multiple)

ApprovedSmall Molecule

Nitrosourea alkylating agent used as standard comparator arm in rGBM trials. Limited efficacy but established as regulatory benchmark.

Tumor Treating Fields (Optune)
low

Novocure

ApprovedDevice

Non-invasive device delivering alternating electric fields to disrupt cell division. Approved for newly diagnosed and rGBM. Compliance-dependent efficacy.

Market Opportunity

Addressable market for GBM therapies

Recurrent Glioblastoma

$3.2B

Growth: 8.5% CAGR

Newly Diagnosed GBM (future expansion)

$4.8B

Growth: 7% CAGR

KOL Simulation

Simulated neuro-oncology KOL responses

KOL Personas

Dr. William Kelly

UT Health San Antonio

high
Improving survival in recurrent GBM beyond current 6–9 month medianValidating Trop-2 as an actionable biomarker in GBMDemonstrating BBB penetration of ADCs in CNS tumorsPublishing Phase 2 results in high-impact journal

Academic Neuro-Oncologist

NCI-Designated Cancer Center

high
Evidence-based treatment selection for rGBMMolecular subtyping to guide therapyParticipation in cooperative group trialsAdvancing immunotherapy approaches in GBM

Scenarios

Phase 2 Primary Analysis Shows OS-6 Benefit

Opportunity

Phase 2 primary analysis demonstrates OS-6 of 55% in Trop-2 positive rGBM, significantly exceeding the 35% historical benchmark. Median OS is 9.2 months. Subgroup analysis shows highest benefit in mesenchymal subtype with Trop-2 H-score > 200.

Gilead Deprioritizes CNS Indications for Trodelvy

Medium

Gilead Sciences announces strategic refocus of Trodelvy development on breast and urothelial cancers, deprioritizing CNS indications. This creates uncertainty about commercial supply for investigator-initiated GBM studies but also reduces competitive pressure.

Simulated Responses

Dr. William Kelly

Strongly advocates for expanding to randomized Phase 3 and seeking partnership for registration-enabling study
A 55% OS-6 rate in biomarker-selected rGBM is the most encouraging signal we've seen in this disease in years. The Trop-2 H-score gives us a rational way to select patients, and the subgroup analysis suggests we can identify patients who benefit most. This warrants a randomized Phase 3.
Single-arm Phase 2 design limits regulatory impact without randomized comparatorNeed cooperative group (Alliance/NRG) to support Phase 3 trialGilead drug supply agreement must be secured long-term

Academic Neuro-Oncologist

Cautiously interested but requires randomized data before changing practice
The data is interesting and the biomarker approach is sound, but we've been burned before in GBM. I need to see a randomized trial before I can recommend this over bevacizumab or clinical trial enrollment. The Trop-2 selection strategy is what makes this different from prior failures.
Single-arm design cannot control for patient selection biasHistorical comparisons in GBM are unreliable due to evolving standard of careBevacizumab also showed promising Phase 2 data but failed to improve OS in Phase 3Need central RANO review to confirm response assessments

Dr. William Kelly

Concerned about long-term drug supply but sees opportunity for academic-led development
Gilead's decision is disappointing but not surprising — GBM is a small market for a company focused on blockbuster oncology. We've always driven this program as an investigator-initiated effort, and we'll continue to do so. The science supports pursuing this regardless of commercial interest.
Drug supply continuity for ongoing Phase 2 and potential Phase 3Without Gilead investment, registration pathway relies entirely on academic fundingNCI or DoD funding would be needed for Phase 3

Risk Assessment

Key risks for sacituzumab govitecan in GBM

Blood-Brain Barrier Limits ADC Delivery

high

ADCs are large molecules (~150 kDa) with inherently limited BBB penetration. While Phase 0 confirmed delivery in contrast-enhancing lesions, non-enhancing infiltrative tumor regions may have intact BBB and reduced drug exposure.

Mitigation: Focus enrollment on patients with contrast-enhancing rGBM. Correlate imaging patterns with response. Explore BBB disruption strategies (focused ultrasound) for future combinations.

Drug Supply Dependency on Gilead

high

As an investigator-initiated study using a commercial drug, supply depends on Gilead's willingness to provide sacituzumab govitecan. Gilead may deprioritize CNS indications or change supply terms.

Mitigation: Maintain strong relationship with Gilead medical affairs. Secure NCI-CTEP as backup supply mechanism. Negotiate multi-year supply agreement tied to study milestones.

Biomarker Screening Limits Eligible Population

medium

Trop-2 H-score ≥ 100 requirement reduces the pool of eligible rGBM patients. Approximately 60–70% of screened patients may qualify, and tissue availability from prior surgery is not guaranteed.

Mitigation: Establish efficient tissue screening workflow. Partner with neuropathology labs for rapid Trop-2 IHC turnaround. Consider expanding to additional neuro-oncology sites.

Single-Arm Phase 2 May Not Support Approval

medium

FDA typically requires randomized data for new indications. A single-arm Phase 2 in rGBM, even with strong OS-6 data, may not be sufficient for supplemental BLA without a randomized confirmatory study.

Mitigation: Design Phase 2 with robust historical comparison methodology. Engage FDA for EOP2 meeting on registration pathway. Plan randomized Phase 3 through cooperative group if Phase 2 is positive.

Emerging GBM Therapies May Shift Standard of Care

low

Other novel approaches in GBM (e.g., CAR-T, neoantigen vaccines, EGFR-targeted ADCs) could change the treatment landscape before sacituzumab GBM data matures.

Mitigation: Monitor competitive landscape closely. Differentiate on biomarker selection and drug repurposing efficiency. Position for combination strategies with emerging agents.

Lifecycle Position

Sacituzumab govitecan across the pharma lifecycle

Strategic Recommendations

SWOT analysis and strategic priorities

Strengths
  • + Repurposing FDA-approved drug with established safety and manufacturing
  • + Phase 0 confirmed intratumoral drug delivery across disrupted BBB
  • + Biomarker-selected approach (Trop-2 H-score) enriches for responders
  • + Investigator-initiated — academic independence from pharma priorities
  • + Addresses devastating unmet need (no new rGBM drugs approved in >10 years)
  • + Interim Phase 2 data shows encouraging OS-6 signal
Weaknesses
  • - Single-arm Phase 2 design limits regulatory impact
  • - Drug supply dependent on Gilead commercial/IIT agreement
  • - Limited funding compared to pharma-sponsored trials
  • - Small enrollment (n=40) limits statistical power
  • - BBB penetration variable based on tumor enhancement pattern
  • - Single-institution lead site limits enrollment speed
Opportunities
  • * First ADC to show meaningful efficacy signal in GBM
  • * Cooperative group (NRG/Alliance) sponsorship for Phase 3
  • * GBM patient advocacy groups are highly motivated for new treatments
  • * Combination with bevacizumab (enhanced BBB disruption) or TTFields
  • * Expansion to brain metastases from TNBC (same drug, Trop-2 target)
  • * NCI-CTEP funding mechanisms for rare/refractory tumor types
Threats
  • ! Gilead may not support CNS development of Trodelvy commercially
  • ! Competing GBM approaches (CAR-T, vaccines, other ADCs) in development
  • ! Historical failure rate of GBM clinical trials is >90%
  • ! Bevacizumab precedent — promising Phase 2 data did not translate to OS benefit in Phase 3
  • ! Insurance coverage challenges for off-label use of approved ADC in GBM
  • ! Limited commercial incentive due to small patient population

Publication Tracker

Key publications for sacituzumab govitecan in GBM

Phase 0 study of sacituzumab govitecan demonstrating intratumoral delivery of SN-38 in recurrent glioblastoma

Kelly WJ, Shah NJ, Bhargav AG et al.

Neuro-Oncology2023original-research

DOI: 10.1093/neuonc/noad123

Trop-2 expression in glioblastoma: a potential target for antibody-drug conjugate therapy

Kelly WJ, Soni DM, Takacs GP et al.

Journal of Neuro-Oncology2022original-research

DOI: 10.1007/s11060-022-04090-5

Interim results of a Phase 2 study of sacituzumab govitecan in Trop-2 positive recurrent glioblastoma

Kelly WJ, Shah NJ, Bhargav AG

SNO Annual Meeting 2024 (Abstract)2024original-research

Sacituzumab govitecan in metastatic triple-negative breast cancer (ASCENT)

Bardia A, Hurvitz SA, Tolaney SM et al.

New England Journal of Medicine2021original-research

DOI: 10.1056/NEJMoa2028485