Trodelvy® Plus Keytruda® Reduces Risk of Disease Progression or Death by 35% Versus Keytruda and Chemotherapy in First-Line PD-L1+ Metastatic Triple-Negative Breast Cancer

– First Pivotal Phase 3 Trial to Show Superiority of a TROP-2 Antibody-Drug Conjugate, Trodelvy, Plus Keytruda Versus Standard of Care in 1L Metastatic TNBC –

– Early Trend in Improvement in Overall Survival Observed –

Gilead Sciences, Inc. (NASDAQ:GILD) today announced Trodelvy^® (sacituzumab govitecan-hziy) plus Keytruda^® (pembrolizumab) reduced the risk of disease progression or death by 35% (HR: 0.65) versus standard of care Keytruda plus chemotherapy in first-line treatment for patients with PD-L1+ (CPS ≥10) metastatic triple-negative breast cancer (TNBC). Trodelvy when given in combination with Keytruda resulted in a median progression-free survival (PFS) of 11.2 months vs 7.8 months when Keytruda was given in combination with chemotherapy. These data from the pivotal Phase 3 ASCENT-04/KEYNOTE-D19 study will be presented today as a late-breaking oral presentation at the 2025 ASCO Annual Congress (Abstract #LBA109).

"These results are an important advancement for patients with PD-L1–positive metastatic triple-negative breast cancer, a population for whom first-line options remain limited," said Sara Tolaney, MD, MPH, Dana-Farber Cancer Institute and primary investigator of the ASCENT-04 study. "By combining sacituzumab govitecan with pembrolizumab, we're seeing meaningful gains in progression-free survival and a promising trend in overall survival—findings that could support a new frontline standard of care for this aggressive disease."

"The ASCENT-04 results build on Gilead's aspiration of transforming the treatment of breast cancer with Trodelvy in earlier lines of therapy," said Dietmar Berger, MD, PhD. "Together with the recently reported clinically meaningful topline results from our first-line monotherapy study, these data reinforce our confidence in Trodelvy's utility both as a single agent and in combination with immunotherapy in the frontline metastatic TNBC setting. We are actively engaging with the FDA to explore a potential regulatory path forward for this combination for the benefit of patients."

For the primary endpoint, the median PFS was 11.2 months (95% CI: 9.3-16.7) with Trodelvy plus Keytruda compared to 7.8 months (95% CI: 7.3-9.3) with Keytruda plus chemotherapy, with a median follow-up of 14 months. A highly statistically significant and clinically meaningful improvement was observed with Trodelvy plus Keytruda (n=221), showing a 35% reduction in the risk of disease progression or death (HR: 0.65; p<0.001) in the intent to treat population compared to standard of care Keytruda plus chemotherapy combination (n=222). The PFS benefit was generally consistent across key prespecified subgroups.

A numerically higher overall response rate was observed for the Trodelvy plus Keytruda combination [60% (95% CI: 52.9-66.3) versus 53% (95% CI: 46.4-59.9)], including 13% and 8% with a complete response, respectively, in the Trodelvy plus Keytruda and Keytruda plus chemotherapy arms. Notably, a substantially longer duration of response was observed with Trodelvy plus Keytruda [16.5 months (95% CI: 12.7-19.5) versus 9.2 months (95% CI: 7.6-11.3)]. Encouraging trends in overall survival (OS) were also observed, but data are immature at the time of PFS primary analysis. Overall survival follow-up remains ongoing and will continue to be monitored as a key secondary endpoint.

The safety profile of Trodelvy plus Keytruda in the ASCENT-04 study was consistent with the known safety profile of each agent. No new safety signals were identified with the combination and the combination did not exacerbate the safety profile of either therapy. The most frequent (≥10% of patients) grade ≥3 treatment-emergent adverse events with Trodelvy plus Keytruda were neutropenia (43%) and diarrhea (10%), and with Keytruda plus chemotherapy were neutropenia (45%), anemia (16%) and thrombocytopenia (14%). Fewer patients discontinued treatment due to adverse events on the Trodelvy plus Keytruda arm than with Keytruda plus chemotherapy (12% vs. 31%).

In addition to ASCENT-04, Gilead on May 23 announced topline results from ASCENT-03 demonstrating a highly statistically significant and clinically meaningful improvement in PFS compared to chemotherapy in patients with first-line metastatic TNBC who are not candidates for PD-1/PD-L1 inhibitors. Detailed results from the ASCENT-03 study will be presented at a future medical meeting and discussed with regulatory authorities.

The use of Trodelvy plus Keytruda in patients with first-line PD-L1+ metastatic TNBC and Trodelvy as monotherapy in patients with first-line metastatic TNBC who are not candidates for PD-1/PD-L1 inhibitors are investigational, and the safety and efficacy of these uses have not been established.

KEYTRUDA^® is a registered trademark of Merck Sharp & Dohme LLC., a subsidiary of Merck & Co., Inc., Rahway, NJ, USA.

About Triple-Negative Breast Cancer with PD-L1+ Tumors

TNBC is the most aggressive type of breast cancer and has historically been difficult to treat, accounting for approximately 15% of all breast cancers. TNBC is diagnosed more frequently in younger and premenopausal women and is more prevalent in Black and Hispanic women. TNBC cells do not have estrogen and progesterone receptors and have limited HER2. Due to the nature of TNBC, treatment options are extremely limited compared with other breast cancer types. TNBC has a higher chance of recurrence and metastases than other breast cancer types. The average time to metastatic recurrence for TNBC is approximately 2.6 years compared with 5 years for other breast cancers, and the relative five-year survival rate is much lower. Among women with mTNBC, the five-year survival rate is 12%, compared with 28% for those with other types of mBC.

Despite progress in treatment, first-line mTNBC has seen limited new approvals in recent years for tumors that express PD-L1+, and additional options are urgently needed. Despite recent advances, over 50% of patients do not receive treatment beyond first-line, reinforcing the urgent need for new options to help improve patient outcomes. Breast cancers expressing PD-L1 are overall more aggressive and associated with reduced survival time.

About the ASCENT-04/KEYNOTE-D19 Study

In 2021, Gilead entered a collaboration with Merck & Co. to investigate sacituzumab govitecan in combination with pembrolizumab in the Phase 3 trial, ASCENT-04/KEYNOTE-D19. The ASCENT-04/KEYNOTE-D19 study is a global, open-label, randomized Phase 3 trial evaluating the efficacy and safety of sacituzumab govitecan in combination with pembrolizumab compared with treatment of chemotherapy plus pembrolizumab in patients with previously untreated, inoperable locally advanced or metastatic triple-negative breast cancer (TNBC) whose tumors express PD-L1. The study enrolled 443 patients across multiple study sites.

Patients were randomized in a 1:1 ratio to receive either sacituzumab govitecan (10 mg/kg intravenously on Days 1 and 8 of a 21-day cycle) plus pembrolizumab (200 mg intravenously on Day 1 of a 21-day cycle) or chemotherapy plus pembrolizumab. The chemotherapy regimen included gemcitabine plus carboplatin, paclitaxel, or nab-paclitaxel. Treatment continued until blinded independent central review (BICR)-verified disease progression or unacceptable toxicity. Patients randomized to chemotherapy were allowed to crossover and receive sacituzumab govitecan upon disease progression.

The primary endpoint of the study is progression-free survival (PFS) as determined by BICR using RECIST v1.1. Secondary endpoints include overall survival (OS), objective response rate (ORR), duration of response (DOR), time to onset of response (TTR), patient-reported outcomes (PROs), and safety.

More information about ASCENT-04/KEYNOTE-D19 is available at ClinicalTrials.gov: NCT05382286.

About Trodelvy

Trodelvy^® (sacituzumab govitecan-hziy) is a first-in-class Trop-2-directed antibody-drug conjugate. Trop-2 is a cell surface antigen highly expressed in multiple tumor types, including in more than 90% of breast and lung cancers. Trodelvy is intentionally designed with a proprietary hydrolyzable linker attached to SN-38, a topoisomerase I inhibitor payload. This unique combination delivers potent activity to both Trop-2 expressing cells and the tumor microenvironment through a bystander effect.

Trodelvy is currently approved in more than 50 countries for second-line or later metastatic triple-negative breast cancer (TNBC) patients and in more than 40 countries for certain patients with pre-treated HR+/HER2- metastatic breast cancer.

Trodelvy is currently being evaluated in multiple ongoing Phase 3 trials across a range of tumor types with high Trop-2 expression. These studies with Trodelvy, both in monotherapy and in combination with pembrolizumab, involve earlier lines of treatment for TNBC and HR+/HER2- breast cancer—including in curative settings—as well as in lung and gynecologic cancers, where previous proof-of-concept studies have demonstrated clinical activity.

INDICATIONS

TRODELVY^® (sacituzumab govitecan-hziy) is a Trop-2-directed antibody and topoisomerase inhibitor conjugate indicated for the treatment of adult patients with:

• Unresectable locally advanced or metastatic triple-negative breast cancer (mTNBC) who have received two or more prior systemic therapies, at least one of them for metastatic disease.
• Unresectable locally advanced or metastatic hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative (IHC 0, IHC 1+ or IHC 2+/ISH–) breast cancer who have received endocrine-based therapy and at least two additional systemic therapies in the metastatic setting.

IMPORTANT SAFETY INFORMATION

BOXED WARNING: NEUTROPENIA AND DIARRHEA

• TRODELVY can cause severe, life-threatening, or fatal neutropenia. Withhold TRODELVY for absolute neutrophil count below 1500/mm³ or neutropenic fever. Monitor blood cell counts periodically during treatment. Primary prophylaxis with G-CSF is recommended for all patients at increased risk of febrile neutropenia. Initiate anti-infective treatment in patients with febrile neutropenia without delay.

• TRODELVY can cause severe diarrhea. Monitor patients with diarrhea and give fluid and electrolytes as needed. At the onset of diarrhea, evaluate for infectious causes and, if negative, promptly initiate loperamide. If severe diarrhea occurs, withhold TRODELVY until resolved to ≤ Grade 1 and reduce subsequent doses.

CONTRAINDICATIONS

• Severe hypersensitivity reaction to TRODELVY.

WARNINGS AND PRECAUTIONS

Neutropenia: Severe, life-threatening, or fatal neutropenia can occur as early as the first cycle of treatment and may require dose modification. Neutropenia occurred in 64% of patients treated with TRODELVY. Grade 3-4 neutropenia occurred in 49% of patients. Febrile neutropenia occurred in 6%. Neutropenic colitis occurred in 1.4%. Primary prophylaxis with G-CSF is recommended starting in the first cycle of treatment in all patients at increased risk of febrile neutropenia, including older patients, patients with previous neutropenia, poor performance status, organ dysfunction, or multiple comorbidities. Monitor absolute neutrophil count (ANC) during treatment. Withhold TRODELVY for ANC below 1500/mm³ on Day 1 of any cycle or below 1000/mm³ on Day 8 of any cycle. Withhold TRODELVY for neutropenic fever. Treat neutropenia with G-CSF and administer prophylaxis in subsequent cycles as clinically indicated or indicated in Table 2 of USPI.

Diarrhea: Diarrhea occurred in 64% of all patients treated with TRODELVY. Grade 3-4 diarrhea occurred in 11% of patients. One patient had intestinal perforation following diarrhea. Diarrhea that led to dehydration and subsequent acute kidney injury occurred in 0.7% of all patients. Withhold TRODELVY for Grade 3-4 diarrhea and resume when resolved to ≤ Grade 1. At onset, evaluate for infectious causes and if negative, promptly initiate loperamide, 4 mg initially followed by 2 mg with every episode of diarrhea for a maximum of 16 mg daily. Discontinue loperamide 12 hours after diarrhea resolves. Additional supportive measures (e.g., fluid and electrolyte substitution) may also be employed as clinically indicated. Patients who exhibit an excessive cholinergic response to treatment can receive appropriate premedication (e.g., atropine) for subsequent treatments.

Hypersensitivity and Infusion-Related Reactions: TRODELVY can cause serious hypersensitivity reactions including life-threatening anaphylactic reactions. Severe signs and symptoms included cardiac arrest, hypotension, wheezing, angioedema, swelling, pneumonitis, and skin reactions. Hypersensitivity reactions within 24 hours of dosing occurred in 35% of patients. Grade 3-4 hypersensitivity occurred in 2% of patients. The incidence of hypersensitivity reactions leading to permanent discontinuation of TRODELVY was 0.2%. The incidence of anaphylactic reactions was 0.2%. Pre-infusion medication is recommended. Have medications and emergency equipment to treat such reactions available for immediate use. Observe patients closely for hypersensitivity and infusion-related reactions during each infusion and for at least 30 minutes after completion of each infusion. Permanently discontinue TRODELVY for Grade 4 infusion-related reactions.

Nausea and Vomiting: TRODELVY is emetogenic and can cause severe nausea and vomiting. Nausea occurred in 64% of all patients treated with TRODELVY and Grade 3-4 nausea occurred in 3% of these patients. Vomiting occurred in 35% of patients and Grade 3-4 vomiting occurred in 2% of these patients. Premedicate with a two or three drug combination regimen (e.g., dexamethasone with either a 5-HT3 receptor antagonist or an NK₁ receptor antagonist as well as other drugs as indicated) for prevention of chemotherapy-induced nausea and vomiting (CINV). Withhold TRODELVY doses for Grade 3 nausea or Grade 3-4 vomiting and resume with additional supportive measures when resolved to Grade ≤ 1. Additional antiemetics and other supportive measures may also be employed as clinically indicated. All patients should be given take-home medications with clear instructions for prevention and treatment of nausea and vomiting.

Increased Risk of Adverse Reactions in Patients with Reduced UGT1A1 Activity: Patients homozygous for the uridine diphosphate-glucuronosyl transferase 1A1 (UGT1A1)*28 allele are at increased risk for neutropenia, febrile neutropenia, and anemia and may be at increased risk for other adverse reactions with TRODELVY. The incidence of Grade 3-4 neutropenia was 58% in patients homozygous for the UGT1A1*28, 49% in patients heterozygous for the UGT1A1*28 allele, and 43% in patients homozygous for the wild-type allele. The incidence of Grade 3-4 anemia was 21% in patients homozygous for the UGT1A1*28 allele, 10% in patients heterozygous for the UGT1A1*28 allele, and 9% in patients homozygous for the wild-type allele. Closely monitor patients with known reduced UGT1A1 activity for adverse reactions. Withhold or permanently discontinue TRODELVY based on clinical assessment of the onset, duration and severity of the observed adverse reactions in patients with evidence of acute early-onset or unusually severe adverse reactions, which may indicate reduced UGT1A1 function.

Embryo-Fetal Toxicity: Based on its mechanism of action, TRODELVY can cause teratogenicity and/or embryo-fetal lethality when administered to a pregnant woman. TRODELVY contains a genotoxic component, SN-38, and targets rapidly dividing cells. Advise pregnant women and females of reproductive potential of the potential risk to a fetus. Advise females of reproductive potential to use effective contraception during treatment with TRODELVY and for 6 months after the last dose. Advise male patients with female partners of reproductive potential to use effective contraception during treatment with TRODELVY and for 3 months after the last dose.

ADVERSE REACTIONS

In the pooled safety population, the most common (≥ 25%) adverse reactions including laboratory abnormalities were decreased leukocyte count (84%), decreased neutrophil count (75%), decreased hemoglobin (69%), diarrhea (64%), nausea (64%), decreased lymphocyte count (63%), fatigue (51%), alopecia (45%), constipation (37%), increased glucose (37%), decreased albumin (35%), vomiting (35%), decreased appetite (30%), decreased creatinine clearance (28%), increased alkaline phosphatase (28%), decreased magnesium (27%), decreased potassium (26%), and decreased sodium (26%).

In the ASCENT study (locally advanced or metastatic triple-negative breast cancer), the most common adverse reactions (incidence ≥25%) were fatigue, diarrhea, nausea, alopecia, constipation, vomiting, abdominal pain, and decreased appetite. The most frequent serious adverse reactions (SAR) (>1%) were neutropenia (7%), diarrhea (4%), and pneumonia (3%). SAR were reported in 27% of patients, and 5% discontinued therapy due to adverse reactions. The most common Grade 3-4 lab abnormalities (incidence ≥25%) in the ASCENT study were reduced neutrophils, leukocytes, and lymphocytes.

In the TROPiCS-02 study (locally advanced or metastatic HR-positive, HER2-negative breast cancer), the most common adverse reactions (incidence ≥25%) were diarrhea, fatigue, nausea, alopecia, and constipation. The most frequent serious adverse reactions (SAR) (>1%) were diarrhea (5%), febrile neutropenia (4%), neutropenia (3%), abdominal pain, colitis, neutropenic colitis, pneumonia, and vomiting (each 2%). SAR were reported in 28% of patients, and 6% discontinued therapy due to adverse reactions. The most common Grade 3-4 lab abnormalities (incidence ≥25%) in the TROPiCS-02 study were reduced neutrophils and leukocytes.

DRUG INTERACTIONS

UGT1A1 Inhibitors: Concomitant administration of TRODELVY with inhibitors of UGT1A1 may increase the incidence of adverse reactions due to potential increase in systemic exposure to SN-38. Avoid administering UGT1A1 inhibitors with TRODELVY.

UGT1A1 Inducers: Exposure to SN-38 may be reduced in patients concomitantly receiving UGT1A1 enzyme inducers. Avoid administering UGT1A1 inducers with TRODELVY.

Please see full Prescribing Information, including BOXED WARNING.

About Gilead Sciences

Gilead Sciences, Inc. is a biopharmaceutical company that has pursued and achieved breakthroughs in medicine for more than three decades, with the goal of creating a healthier world for all people. The company is committed to advancing innovative medicines to prevent and treat life-threatening diseases, including HIV, viral hepatitis, COVID-19, cancer, and inflammation. Gilead operates in more than 35 countries worldwide, with headquarters in Foster City, Calif.

Forward-Looking Statements

This press release includes forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 that are subject to risks, uncertainties and other factors, including Gilead's ability to initiate, progress or complete clinical trials or studies within currently anticipated timelines or at all, and the possibility of unfavorable results from ongoing and additional clinical trials or studies, including those involving Trodelvy (such as ASCENT-03, ASCENT-04 and ASCENT-05); uncertainties relating to regulatory applications and related filing and approval timelines, including potential applications for programs and/or indications currently under evaluation; the possibility that Gilead may make a strategic decision to discontinue development of these programs and, as a result, these programs may never be successfully commercialized for the indications currently under evaluation; and any assumptions underlying any of the foregoing. These and other risks, uncertainties and factors are described in detail in Gilead's Quarterly Report on Form 10-Q for the quarter ended March 31, 2025, as filed with the U.S. Securities and Exchange Commission. These risks, uncertainties and other factors could cause actual results to differ materially from those referred to in the forward-looking statements. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. The reader is cautioned that any such forward-looking statements are not guarantees of future performance and involve risks and uncertainties and is cautioned not to place undue reliance on these forward-looking statements. All forward-looking statements are based on information currently available to Gilead, and Gilead assumes no obligation and disclaims any intent to update any such forward-looking statements.

Trodelvy, Gilead and the Gilead logo are trademarks of Gilead Sciences, Inc., or its related companies.

U.S. Prescribing Information for Trodelvy, including BOXED WARNING, is available at www.gilead.com.

For more information about Gilead, please visit the company's website at www.gilead.com, follow Gilead on X/Twitter (@Gilead Sciences) and LinkedIn (@Gilead-Sciences).

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Blair Baumwell, Media

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Jacquie Ross, Investors

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