Clinical Research FAQs

Clinical research studies are conducted to determine if potential new medicines are safe and whether they work. Clinical research studies are performed according to government regulations that help protect the safety and rights of study participants.

A clinical investigator is a medical researcher in charge of conducting a clinical study and ensuring the well-being of study volunteers. The investigators conducting the PURPOSE 2 study are all qualified licensed doctors and medical specialists.

An investigational drug, or research study drug, is a drug that has not yet been approved by the Food and Drug Administration (FDA), or other regulatory agencies for prescription by doctors. The investigational medicine in the PURPOSE 2 study is lenacapavir.

Yes, participation in any clinical research study is completely voluntary. If you decide to stop participating at any time, your exit will not affect the medical care you would otherwise receive.

Informed consent is the process of learning the key facts and details about a clinical research study. This information will be provided to you before you decide to participate and as new information becomes available during your continued participation throughout the study. Once you have read the informed consent form and understand the details, including the risks and benefits, you can decide whether to sign the document. The informed consent process also includes opportunities for you to ask questions about the study. No study-related procedures will take place without a signed informed consent form.


This clinical study is being conducted to evaluate the safety and efficacy of an investigational medicine, lenacapavir, to reduce the chance of getting HIV through sex—also known as pre-exposure prophylaxis (PrEP).

Sex assigned at birth and gender are separate entities. When we are born, we are assigned a sex based on our biological characteristics. Most of us are assigned male or female, with a small number being intersex (having biological characteristics of both male and female). After we are born, we begin to develop gender identity, which is one’s internal sense of being a man, a woman, neither, or both. Some of us are cisgender, meaning that our sex assigned at birth and gender identity are the same. Others of us are transgender, meaning that our sex assigned at birth and gender identity are not the same. Still others of us do not identify with either traditional gender category, and may identify as gender nonbinary, gender-fluid, or a third gender.   PURPOSE 2 will enroll cisgender men, transgender women, transgender men, and gender nonbinary individuals who have receptive anal sex with partners assigned male at birth.   For more information, consider visiting

Your answers to the questions in the online prescreening form will determine if you meet certain key criteria that are required to participate in the PURPOSE 2 study. If you meet these criteria, you may then contact a participating doctor’s office of your choice using their contact details on our website. Their staff will answer any questions you may have and will discuss the next steps to further determine whether you meet all of the criteria for participation. Not all people who complete the online prescreening form will be able to participate in this study.   Do you qualify?

If you meet the criteria in the prescreening form and then contact a participating doctor’s office, you will have a single visit where the staff at the doctor’s office will ask you to review and sign an informed consent form that explains more about the study. During that visit you will get an HIV test and other lab tests. Then the staff at the doctor’s office will ask more questions and run some medical tests to see if you meet all eligibility criteria to participate in the clinical research study. If you do not have HIV and meet the other eligibility criteria, you can choose to participate in the second part of the study. If you are confirmed to have HIV, we will link you to HIV care in your community.   Feel free to discuss your study-related medical care with the study doctor or staff at any time during the course of the research study. It is important to take the investigational medicine as prescribed. You will answer questions regarding how you feel during your participation and whether the investigational study medicine has been taken at the appropriate times. Participants are encouraged to discuss study participation with their primary care doctor.

The first part of the study is a single visit. The second part of the study will last for at least 1 year and up to 3 years. The visits are 4-13 weeks apart, with 4-8 visits per year.

Approximately 3,000 people worldwide will be enrolled in the PURPOSE 2 study. This study is looking for cisgender men, transgender women, transgender men, and gender nonbinary individuals who have receptive anal sex with partners assigned male at birth, who have not had an HIV test in the past 3 months, and are at least 18 years old.

Reimbursement for study-related travel may be available depending on local practice in your country.

If you participate, study-related doctors' visits, monitoring of your health, and the study medicine will be provided to you at no cost. You do not need health insurance to participate. The study staff at the participating site will be able to answer any questions you may have.

The choice to participate in this study is entirely yours. Your primary care doctor does not have to give his or her permission or a referral for you to participate in this study. However, you should tell your primary care physician about your participation and keep him or her informed about the study. You should also keep the study doctor informed if your primary care physician changes or if there are other changes to your health during the study.

A long-term extension study is a clinical study that allows participants to continue on the study medicine after they have finished their participation in the original study. After completion of PURPOSE 2, participants may have the opportunity to enroll in a long-term extension study of lenacapavir for pre-exposure prophylaxis (PrEP).

A placebo looks the same as the study medicine but does not contain any active ingredients. The use of a placebo is important in clinical research studies, because it allows researchers to determine how well the active study medicine is working.   Everyone in PURPOSE 2 will receive one active medicine and one placebo. Neither you nor the study doctor will be able to choose or know which study group you are in. However, the study doctor can access this information if there is an emergency or if it is necessary to know for your health.

You could experience side effects associated with the study medicine. The study staff will discuss the known risks in detail with you before you decide whether to participate.

After a clinical study is complete, all of the information is collected and analyzed to help determine the study medicine’s safety and efficacy. Please consult with your study doctor or primary healthcare provider to determine your HIV prevention options after completing the study.

The PURPOSE 2 study is being conducted by trained, qualified, and licensed medical doctors worldwide.

Gilead Sciences, Inc. is developing the PURPOSE 2 study medicine and sponsoring this clinical research study. GILEAD is a trademark of Gilead Sciences, Inc. All other trademarks referenced in this document are the property of their respective owners.

For illustrative purposes only.

What's in It for You?

People who qualify to take part in the PURPOSE 2 study can expect to:

  • Be a part of determining whether an investigational injectable PrEP medicine reduces the chance of getting HIV through sex
  • Receive study drug and monitoring from a local study doctor at no cost
  • Receive reimbursement for study-related travel expenses
  • Be eligible to participate in an extension phase of the study
For illustrative purposes only.

PURPOSE 2 Questionnaire

Thank you for your interest in participating in the PURPOSE 2 study.

Your privacy matters to us. Note that your answers will only be used to let you know whether or not you qualify, and will not be stored or tracked in any way.

*If you are 16 or 17 years old, please contact your local clinical trial site and learn about their requirements.