Drug information

Other Names:
MGN1703, dSLIM-30L1, double-stem-loop immunomodulator 30L1
Drug Class:
Latency-Reversing Agents
Registry Number:
1548439-51-5 (CAS)
Chemical Class:
Mologen AG
Phase of Development:

Lefitolimod is in Phase 2a development as an HIV therapeutic.

(Compound details obtained from ChemIDplus Advanced,1 Clinical Infectious Diseases article,2 NCI Drug Dictionary,3 Mologen AG website,4 and ClinicalTrials.gov5)

What is lefitolimod?What is lefitolimod?

What is lefitolimod?

Lefitolimod is an investigational drug that is being studied as part of a strategy to cure HIV infection. Lefitolimod belongs to a general group of HIV drugs called latency-reversing agents. There are different types of latency-reversing agents. Lefitolimod is a type of latency-reversing agent called a toll-like receptor agonist.2

To learn about how investigational drugs are tested during clinical trials, read the HIVinfo What is an Investigational HIV Drug? and HIV/AIDS Clinical Trials fact sheets.

How do latency-reversing agents work?How do latency-reversing agents work?

How do latency-reversing agents work?

Currently, there is no cure for HIV infection. One of the main obstacles to curing HIV infection is that the virus can remain hidden and inactive (latent) inside certain cells of the immune system (such as resting CD4 cells) for many months or even years. The cells where latent HIV hides are known as the latent HIV reservoir. Because HIV in this latent state is inactive, the immune system cannot detect the virus, and the antiretroviral (ARV) drugs that are used to treat HIV have no effect on it.6-8

Latency-reversing agents work by drawing HIV out of its latent state within resting CD4 cells. Once the latent HIV is reactivated, the CD4 cells that harbor the virus may be more likely to be recognized and killed by the body’s immune system or may be killed by certain HIV therapies, such as those that can enhance the body’s immune response to HIV. Researchers hope that the combined use of lefitolimod and other HIV-fighting strategies, including ongoing antiretroviral therapy (ART), may fully eliminate HIV from the body.6-8 To learn more, see the HIVinfo What is a Latent HIV Reservoir? fact sheet.

Select Clinical Trials

Select Clinical Trials

Study Names: TEACH study; NCT02443935
Phase: 1b/2a
Status: This study has been completed.
Location: Denmark
Purpose: The purpose of this study was to investigate whether lefitolimod could reactivate latent HIV, improve immune responses in participants with HIV, reduce the size of the latent HIV reservoir, and delay the time to a viral rebound after a structured treatment interruption of ART. The study also assessed the safety of lefitolimod.2,9

Study Name: NCT04357821
Phase: 1/2
Status: This study is currently recruiting participants.
Location: United States
Purpose: The purpose of this study is to evaluate whether using combination therapy can control viral load levels when participants undergo a structured treatment interruption of ART. Combination therapy includes (1) therapeutic HIV vaccines, (2) broadly neutralizing antibodies (bNAbs) VRC07-523LS and 10-1074, and (3) lefitolimod.10

Study Names: TITAN; NCT03837756
Phase: 2a
Status: This status of this study is unknown.
Location: United States, Australia, and Denmark
Purpose: The purpose of this study is to evaluate the safety of lefitolimod administered with the bNAbs 3BNC117 and 10-1074 and to evaluate whether this combination therapy can delay the time to viral rebound after a structured treatment interruption of ART.5

For more details on the studies listed above, see the Health Professional version of this drug summary.

What side effects might lefitolimod cause?What side effects might lefitolimod cause?

What side effects might lefitolimod cause?

One goal of HIV research is to identify new drugs that have fewer side effects. In the first part of the TEACH study (NCT02443935) discussed under the previous question, the most commonly reported side effect related to lefitolimod was mild redness (erythema) around the injection site, which resolved on its own. All drug-related side effects that occurred during the study were mild, except for four cases of low white blood cell counts (neutropenia). All side effects, including the cases of neutropenia, went away on their own.2,9

The types of side effects that occurred during the second part of the TEACH study were reported to be similar to previously reported side effects for lefitolimod.11

Because lefitolimod is still being studied, information on possible side effects of the drug is not complete. As testing of lefitolimod continues, additional information on possible side effects will be gathered.

Where can I get more information about clinical trials studying lefitolimod?Where can I get more information about clinical trials studying lefitolimod?

Where can I get more information about clinical trials studying lefitolimod?

More information about lefitolimod-related research studies is available from ClinicalTrials.gov.

Some clinical trials may be looking for volunteer participants. Your health care provider can help you decide whether participating in a clinical trial is right for you. For more information, visit NIH Clinical Research Trials and You.



  1. United States National Library of Medicine. ChemIDplus Advanced: Lefitolimod. https://chem.nlm.nih.gov/chemidplus/rn/1548439-51-5. Accessed March 8, 2021
  2. Vibholm L, Schleimann MH, Højen JF, et al. Short-course Toll-like receptor 9 agonist treatment impacts innate immunity and plasma viremia in individuals with human immunodeficiency virus infection. Clin Infect Dis. 2017;64(12). https://academic.oup.com/cid/article/64/12/1686/3064483. Accessed March 8, 2021
  3. National Cancer Institute (NCI). NCI Drug Dictionary: TLR9 agonist MGN1703. https://www.cancer.gov/publications/dictionaries/cancer-drug/def/lefitolimod. Accessed March 8, 2021
  4. Mologen AG website. Product pipeline. https://www.mologen.com/en/pipeline. Accessed March 8, 2021
  5. University of Aarhus. Combining a TLR9 agonist with broadly neutralizing antibodies for reservoir reduction and immunological control of HIV infection: an investigator-initiated randomized, placebo-controlled, Phase IIa trial. In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on February 7, 2019. NLM Identifier: NCT03837756. https://clinicaltrials.gov/ct2/show/NCT03837756. Accessed March 8, 2021
  6. Siliciano RF, Greene WC. HIV latency. Cold Spring Harb Perspect Med. 2011;1(1):a007096.
  7. Rasmussen TA, Tolstrup M, Winckelmann A, Østergaard L, Søgaard OS. Eliminating the latent HIV reservoir by reactivation strategies. Hum Vaccines Immunother. 2013;9(4):790–799.
  8. National Institute of Allergy and Infectious Diseases (NIAID). HIV viral eradication. https://www.niaid.nih.gov/diseases-conditions/hiv-viral-eradication. Accessed March 8, 2021
  9. University of Aarhus. Toll-like receptor 9 enhancement of antiviral immunity in chronic HIV-1 infection: a Phase 1b/2a trial. In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on April 30, 2015. NLM Identifier: NCT02443935. https://clinicaltrials.gov/ct2/show/NCT02443935. Accessed March 8, 2021
  10. University of California, San Francisco. Combinatorial therapy with a therapeutic conserved element DNA vaccine, MVA vaccine boost, TLR9 agonist and broadly neutralizing antibodies: a proof-of-concept study aimed at inducing an HIV remission. In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on April 18, 2020. NLM Identifier: NCT04357821. https://clinicaltrials.gov/ct2/show/NCT04357821. Accessed March 8, 2021
  11. Vibholm LK, Frattari G, Schleimann MH, et al. Effect of 24 weeks TLR9 agonist therapy on CTL responses and viral rebound during ATI. Poster presented at: Conference on Retroviruses and Opportunistic Infections (CROI): March 4-7, 2018; Boston, MA. Poster 357. https://2jg4quetidw2blbbq2ixwziw-wpengine.netdna-ssl.com/wp-content/uploads/sites/2/posters/2018/1430_Vibholm_357.pdf. Accessed March 8, 2021

Last Reviewed: March 8, 2021