New Data for Trodelvy Demonstrate Clinical Efficacy Across Trop-2 Expression Levels in HR+/HER2- Metastatic Breast Cancer

Late-Breaking TROPiCS-02 Analysis Shows that Trodelvy Demonstrates Consistent Efficacy Across Trop-2 Expression Levels –

– Trop-2 is Highly Expressed in 90% of Breast Cancers –

– Trodelvy is Currently Under Priority Review with the U.S. FDA for Pre-Treated HR+/HER2- Metastatic Breast Cancer –

Gilead Sciences, Inc. (Nasdaq: GILD) today announced new data from a post-hoc analysis from the Phase 3 TROPiCS-02 study evaluating Trodelvy ^® (sacituzumab govitecan-hziy; SG) versus comparator chemotherapy (physicians' choice of chemotherapy, TPC) in patients with HR+/HER2- metastatic breast cancer who progressed on endocrine-based therapies and at least two chemotherapies. In the analysis, Trodelvy improved progression-free survival (PFS), overall survival (OS) and objective response rate (ORR) compared with TPC across Trop-2 expression levels. Details of the late-breaking abstract will be presented today at the 2022 San Antonio Breast Cancer Symposium (SABCS, Abstract #GS1-11).

"Sacituzumab govitecan improved both progression-free survival and overall survival in pre-treated HR+/HER2- metastatic breast cancer in the Phase 3 TROPiCS-02 study compared to standard chemotherapy options. This post-hoc analysis demonstrates that the level of Trop-2 expression on an individual's tumor did not impact sacituzumab govitecan efficacy," said Dr. Hope Rugo, Professor of Medicine and Director, Breast Oncology and Clinical Trials Education at the University of California San Francisco Comprehensive Cancer Center, U.S. "These data can give us confidence in the potential benefit of sacituzumab govitecan for patients with endocrine-resistant metastatic breast cancer who have progressed on available chemotherapies, across Trop-2 expression levels."

Trop-2, a protein found on the surface of cancer cells, is involved in several cellular processes regulating cancer growth and invasion. It is highly expressed in most human solid tumors, including more than 90% of breast cancers. In the TROPiCS-02 study, Trop-2 expression was measured by immunohistochemistry and expressed as a histochemical score (H-score; range, 0-300). Efficacy outcomes were assessed across H-score groups, including those with very low Trop-2 expression. Across each H-score subgroup, Trodelvy demonstrated improved PFS, OS and ORR compared to TPC, which is consistent with the PFS, OS and ORR in the TROPiCS-02 intention-to-treat population.

"The prognosis for patients with pre-treated HR+/HER2- metastatic breast cancer who have developed resistance to endocrine-based therapies has been poor, and these TROPiCS-02 study results demonstrate clinical efficacy with Trodelvy, across Trop-2 expression levels," said Bill Grossman, MD, PhD, Senior Vice President, Therapeutic Area Head, Gilead Oncology. "Our ambition is to continue our impact beyond our current approval in second-line metastatic TNBC, and we look forward to advancing discussions with the U.S. FDA and global health authorities to help bring Trodelvy to more people living with metastatic breast cancer."

The safety profile for Trodelvy in TROPiCS-02 was consistent with prior studies, with no new safety signals identified in this population.

Detailed statistically significant and clinically meaningful PFS and OS results from the Phase 3 TROPiCS-02 study were presented at ASCO 2022 and ESMO 2022 , respectively. Based on these data, the U.S. Food and Drug Administration (FDA) accepted for priority review the supplemental Biologics License Application (sBLA) for Trodelvy in adult patients with unresectable locally advanced or metastatic HR+/HER2- (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. The Prescription Drug User Fee Act (PDUFA) target action date is currently set for February 2023.

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

Summary of post-hoc analysis results by Trop-2 expression

Additional Abstracts across Gilead's Breast Cancer Franchise at 2022 SABCS:

Gilead is also presenting a number of other abstracts at the congress, including patient-reported outcomes data from TROPiCS-02, and in preclinical research and trials in progress in metastatic triple-negative breast cancer (TNBC). Accepted abstracts at SABCS 2022 include (all times CDT):

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 40 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 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 FDA approval of the sBLA for Trodelvy for treatment of HR+/HER2- metastatic breast cancer, and pending or potential applications for the treatment of metastatic TNBC, HR+/HER2- metastatic breast cancer, metastatic UC, metastatic NSCLC, metastatic 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 September 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.

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