New TROPiCS-02 Data in HR+/HER2- Metastatic Breast Cancer Patients Demonstrates Progression-Free Survival Benefit of Trodelvy® Regardless of Their HER2 Status

-- Progression-Free Survival Efficacy of Trodelvy Consistent with That Observed in the TROPiCS-02 Intention-to-Treat Population --

-- Results Presented at ESMO 2022 Highlight Trodelvy as a Potential Treatment Option in HR+/HER2-Low and IHC0 Status Metastatic Breast Cancer --

Gilead Sciences, Inc. (Nasdaq: GILD) today announced new data from a post hoc subgroup analysis from the Phase 3 TROPiCS-02 study evaluating Trodelvy ^® (sacituzumab govitecan-hziy) versus comparator chemotherapies (physicians' choice of chemotherapy, TPC) in patients with HR+/HER2- metastatic breast cancer who progressed on endocrine-based therapies and at least two chemotherapies. The analysis examined progression-free survival (PFS) in the intention-to-treat population by HER2-immunohistochemistry (IHC) status, and the results demonstrated that Trodelvy improved median PFS vs. TPC in both HER2-low (IHC1+ and IHC2+/ISH-negative) and IHC0 groups.

Summary of results:

Detailed findings will be presented at a mini-oral session (Abstract #1362) during the European Society for Medical Oncology (ESMO) Congress 2022 in the Évry Auditorium, Paris Expo Porte de Versailles, on September 10.

"These data demonstrate Trodelvy's efficacy across HER2-low and IHC0 status in pre-treated metastatic breast cancer patients in the TROPiCS-02 trial," said Professor Peter Schmid, Professor of Cancer Medicine; Centre Lead, Centre of Experimental Cancer Medicine; Director, Barts Breast Cancer Centre. "Once patients have developed resistance to endocrine-based therapies, their prognosis is extremely poor. The results highlight the potential for Trodelvy as a treatment option for people living with pre-treated HR+/HER2- metastatic breast cancer, regardless of their HER2-negative status."

"These results show Trodelvy improved progression-free survival regardless of HER2 status in this pre-treated patient population and reinforce the strength of clinical activity in a population where need is highest," said Bill Grossman, MD, PhD, Senior Vice President, Therapeutic Area Head, Gilead Oncology. "Trodelvy is already transforming the standard of care in second-line metastatic triple-negative breast cancer, and we're excited about its potential in other breast cancers where there is significant need for new treatment options."

In the study, HER2 negativity was defined per American Society of Clinical Oncology (ASCO) and the College of American Pathologists (CAP) criteria as immunohistochemistry (IHC) score of 0, IHC 1+ or IHC 2+ with a negative in-situ hybridization (ISH) test.

Trodelvy has not been approved by any regulatory agency for the treatment of HR+/HER2- metastatic breast cancer. Its safety and efficacy have not been established for this indication. Gilead has submitted a supplemental Biologics License Application (sBLA) to the U.S. Food and Drug Administration (FDA) based on data from TROPiCS-02; these data will also be shared with health authorities outside the U.S.

Sacituzumab govitecan is currently included in the National Comprehensive Cancer Network ^® (NCCN ^® ) Clinical Practice Guidelines in Oncology (NCCN Guidelines ^® ) ⁱ . This includes a Category 1 recommendation for use in adult patients with second-line metastatic triple-negative breast cancer (defined as those who received at least two prior therapies, with at least one line for metastatic disease). It also has a Category 2A preferred recommendation for investigational use in HR+/HER2- advanced breast cancer after prior treatment including endocrine therapy, a CDK4/6 inhibitor and at least two lines of chemotherapy.

Trodelvy has a Boxed Warning for severe or life-threatening neutropenia and severe diarrhea; please see below for additional Important Safety Information.

About HR+/HER2- Breast Cancer

Hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer is the most common type of breast cancer and accounts for approximately 70% of all new cases, or nearly 400,000 diagnoses worldwide each year. Almost one in three cases of early-stage breast cancer eventually become metastatic, and among patients with HR+/HER2- metastatic disease, the five-year relative survival rate is 30%. As patients with HR+/HER2- metastatic breast cancer become resistant to endocrine-based therapy, their primary treatment option is limited to single-agent chemotherapy. In this setting, it is common to receive multiple lines of chemotherapy regimens over the course of treatment, and the prognosis remains poor.

About the TROPiCS-02 Study

The TROPiCS-02 study is a global, multicenter, open-label, Phase 3 study, randomized 1:1 to evaluate Trodelvy versus physicians' choice of chemotherapy (eribulin, capecitabine, gemcitabine, or vinorelbine) in 543 patients with HR+/HER2- metastatic breast cancer who were previously treated with endocrine therapy, CDK4/6 inhibitors and two to four lines of chemotherapy for metastatic disease. The primary endpoint is progression-free survival per Response Evaluation Criteria in Solid Tumors (RECIST 1.1) as assessed by blinded independent central review (BICR) for participants treated with Trodelvy compared to those treated with chemotherapy. Secondary endpoints include overall survival, overall response rate, clinical benefit rate and duration of response, as well as assessment of safety and tolerability and quality of life measures. More information about TROPiCS-02 is available at https://clinicaltrials.gov/ct2/show/NCT03901339 .

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 bladder 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 microenvironment.

Trodelvy is approved in more than 35 countries, with multiple additional regulatory reviews underway worldwide, for the treatment of adult patients with unresectable locally advanced or metastatic triple-negative breast cancer (TNBC) who have received two or more prior systemic therapies, at least one of them for metastatic disease. Trodelvy is also approved in the U.S. under the accelerated approval pathway for the treatment of adult patients with locally advanced or metastatic urothelial cancer (UC) who have previously received a platinum-containing chemotherapy and either programmed death receptor-1 (PD-1) or programmed death-ligand 1 (PD-L1) inhibitor.

Trodelvy is also being developed for potential investigational use in other TNBC and metastatic UC populations, as well as a range of tumor types where Trop-2 is highly expressed, including hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) metastatic breast cancer, metastatic non-small cell lung cancer (NSCLC), metastatic small cell lung cancer (SCLC), head and neck cancer, and endometrial cancer.

U.S. Indications for Trodelvy

In the United States, Trodelvy is indicated for the treatment of:

• Adult patients with unresectable locally advanced or metastatic TNBC who have received two or more prior systemic therapies, at least one of them for metastatic disease.
• Adult patients with locally advanced or metastatic UC who have previously received a platinum-containing chemotherapy and either programmed death receptor-1 (PD-1) or programmed death-ligand 1 (PD-L1) inhibitor. This indication is approved under accelerated approval based on tumor response rate and duration of response. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial.

U.S. Important Safety Information for Trodelvy

BOXED WARNING: NEUTROPENIA AND DIARRHEA

• Severe or life-threatening neutropenia may occur. Withhold Trodelvy for absolute neutrophil count below 1500/mm ³ or neutropenic fever. Monitor blood cell counts periodically during treatment. Consider G-CSF for secondary prophylaxis. Initiate anti-infective treatment in patients with febrile neutropenia without delay.
• Severe diarrhea may occur. Monitor patients with diarrhea and give fluid and electrolytes as needed. Administer atropine, if not contraindicated, for early diarrhea of any severity. At the onset of late 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 and may require dose modification. Neutropenia occurred in 61% of patients treated with Trodelvy. Grade 3-4 neutropenia occurred in 47% of patients. Febrile neutropenia occurred in 7%. Withhold Trodelvy for absolute neutrophil count below 1500/mm ³ on Day 1 of any cycle or neutrophil count below 1000/mm ³ on Day 8 of any cycle. Withhold Trodelvy for neutropenic fever.

Diarrhea: Diarrhea occurred in 65% of all patients treated with Trodelvy. Grade 3-4 diarrhea occurred in 12% of patients. One patient had intestinal perforation following diarrhea. Neutropenic colitis occurred in 0.5% of 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: Serious hypersensitivity reactions including life-threatening anaphylactic reactions have occurred with Trodelvy. Severe signs and symptoms included cardiac arrest, hypotension, wheezing, angioedema, swelling, pneumonitis, and skin reactions. Hypersensitivity reactions within 24 hours of dosing occurred in 37% of patients. Grade 3-4 hypersensitivity occurred in 2% of patients. The incidence of hypersensitivity reactions leading to permanent discontinuation of Trodelvy was 0.3%. The incidence of anaphylactic reactions was 0.3%. Pre-infusion medication is recommended . Observe patients closely for hypersensitivity and infusion-related reactions during each infusion and for at least 30 minutes after completion of each infusion. Medication to treat such reactions, as well as emergency equipment, should be available for immediate use. Permanently discontinue Trodelvy for Grade 4 infusion-related reactions.

Nausea and Vomiting: Nausea occurred in 66% of all patients treated with Trodelvy and Grade 3 nausea occurred in 4% of these patients. Vomiting occurred in 39% of patients and Grade 3-4 vomiting occurred in 3% 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 67% in patients homozygous for the UGT1A1*28, 46% in patients heterozygous for the UGT1A1*28 allele and 46% in patients homozygous for the wild-type allele. The incidence of Grade 3-4 anemia was 25% in patients homozygous for the UGT1A1*28 allele, 10% in patients heterozygous for the UGT1A1*28 allele, and 11% 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 ASCENT study (IMMU-132-05) , the most common adverse reactions (incidence ≥25%) were fatigue, neutropenia, diarrhea, nausea, alopecia, anemia, 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 TROPHY study (IMMU-132-06) , the most common adverse reactions (incidence ≥25%) were diarrhea, fatigue, neutropenia, nausea, any infection, alopecia, anemia, decreased appetite, constipation, vomiting, abdominal pain, and rash. The most frequent serious adverse reactions (SAR) (≥5%) were infection (18%), neutropenia (12%, including febrile neutropenia in 10%), acute kidney injury (6%), urinary tract infection (6%), and sepsis or bacteremia (5%). SAR were reported in 44% of patients, and 10% discontinued due to adverse reactions. The most common Grade 3-4 lab abnormalities (incidence ≥25%) in the TROPHY study were reduced neutrophils, leukocytes, and lymphocytes.

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 substantially 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 and cancer. Gilead operates in more than 35 countries worldwide, with headquarters in Foster City, California.

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 within currently anticipated timelines or at all, and the possibility of unfavorable results from ongoing or additional clinical trials, including those involving Trodelvy; uncertainties relating to regulatory applications for Trodelvy and related filing and approval timelines, including with respect to the pending sBLA for Trodelvy, and pending or potential applications for the treatment of metastatic TNBC, mUC, HR+/HER2- breast cancer, NSCLC, SCLC, head and neck cancer, and endometrial cancer, in the currently anticipated timelines or at all; Gilead's ability to receive regulatory approvals for such indications in a timely manner or at all, and the risk that any such approvals may be subject to significant limitations on use; the possibility that Gilead may make a strategic decision to discontinue development of Trodelvy for such indications and as a result, Trodelvy may never be commercialized for these indications; and any assumptions underlying any of the foregoing. These and other risks, uncertainties and other factors are described in detail in Gilead's Quarterly Report on Form 10-Q for the quarter ended June 30, 2022, 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.

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

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

For more information about Gilead, please visit the company's website at www.gilead.com , follow Gilead on Twitter (@GileadSciences) or call Gilead Public Affairs at 1-800-GILEAD-5 or 1-650-574-3000.

ⁱ Referenced with permission from the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines ^® ) for Breast Cancer Version 4.2022. © National Comprehensive Cancer Network, Inc. 2022. All rights reserved. Accessed August 2022. To view the most recent and complete version of the guideline, go online to NCCN.org. NCCN makes no warranties of any kind whatsoever regarding their content, use or application and disclaims any responsibility for their application or use in any way.

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Jacquie Ross, Investors
investor_relations@gilead.com

Nathan Kaiser, Media
Nathan.kaiser@gilead.com