A Study to Evaluate the Safety and Efficacy of Adding Enfuvirtide to Oral Highly Active Antiretroviral Therapy (HAART) in Human Immunodeficiency Virus (HIV) Patients With Prior Treatment Experience

This study consisted of two phases. In the Induction phase patients were randomized at
Baseline 1 (BL1) in a 1:2 ratio to receive:

- I1: HAART or

- I2: Enfuvirtide (90 mg twice a day) + HAART.

Participants who achieved viral suppression < 50 copies/mL by week 24, confirmed by week 28
or earlier, qualified to enter the Maintenance Phase which started at Baseline 2 (BL2), four
weeks after confirmation of response. The Maintenance Phase consisted of three treatment
groups:

- M1: HAART continued (patients from I1)

Patients on ENF+HAART (I2) were re-randomized (at a 1:1 ratio) at BL2 to:

- M2: Enfuvirtide stopped and HAART continued

- M3: Enfuvirtide + HAART continued.

The duration of the Maintenance Phase was from BL2 up to 48 weeks after BL1. BL2 could start
at the earliest at Week 12 and at the latest Week 32.

Inclusion Criteria:

- HIV-1 infected adults >=18 years of age;

- currently on antiretroviral (ARV) therapy;

- previously treated with 2 or 3 different antiretroviral classes;

- HIV-1 Ribonucleic acid (RNA) >=1,000 copies/mL;

- Cluster differentiation antigen four (CD4) lymphocyte count >=200 cells/mm^3;

- females of childbearing potential must be willing to use a reliable form of effective
barrier contraception for the duration of the study and for 30 days after the last
dose of study drug.

Exclusion Criteria:

- history of prior use of enfuvirtide or T-1249;

- women who are pregnant, breastfeeding or planning to become pregnant during the
study;

- active, untreated opportunistic infection;

- patients on treatment interruption, or patients interrupting ARV therapy within 4
weeks of screening or during the screening period for reasons either than toxicity
management.