hTERT vaccine V934/V935

Drug Overview

The hTERT vaccine V934/V935 (also known as the V934/V935 DNA/Adenoviral prime-boost vaccine) is an investigational, multi-component immunotherapy designed to trigger a potent and durable immune response against cancer cells. It specifically targets human telomerase reverse transcriptase (hTERT), the catalytic subunit of the enzyme telomerase.

Telomerase is often called the “immortality enzyme” because it is overexpressed in more than 85% of all human cancers, allowing malignant cells to maintain their DNA and divide indefinitely. In contrast, telomerase is largely absent or expressed at very low levels in most normal adult cells, making it an ideal “universal” target for cancer vaccination.

Developed by Merck & Co. (MSD), the V934/V935 regimen is a “heterologous prime-boost” strategy. It uses two different delivery vehicles (DNA and a viral vector) to “prime” and then “boost” the immune system’s ability to hunt down telomerase-positive cancer cells.

• Generic Name: V934 (DNA component) and V935 (Adenoviral component).
• Drug Class: Therapeutic Cancer Vaccine / Active Immunotherapy.
• Target: hTERT (Human Telomerase Reverse Transcriptase).
• Platform: Heterologous Prime-Boost (DNA Plasmid and Adenovirus Type 6).
• Route of Administration: Intramuscular (IM) injection.
• FDA Approval Status: Investigational. As of March 2026, the V934/V935 regimen is not FDA-approved. It has completed Phase I clinical trials for advanced solid tumors and is being evaluated in various combination strategies.

What Is It and How Does It Work? (Mechanism of Action)

The V934/V935 vaccine utilizes a “relay race” approach to immune activation, using two distinct stages to maximize the number of “Killer T-cells” in the body.

1. The Prime: V934 (DNA Plasmid)

The first stage involves V934, a DNA plasmid that carries the genetic code for an inactive version of hTERT.

• When injected into the muscle, the DNA enters local cells and instructs them to produce hTERT proteins.
• These proteins are then “shown” to the immune system, creating a baseline level of recognition. This is the “Priming” phase.

2. The Boost: V935 (Adenoviral Vector)

The second stage involves V935, which uses a modified, non-replicating Adenovirus Type 6 (Ad6) as a delivery vehicle.

• This virus is engineered to carry the hTERT gene.
• Because the body recognizes the adenovirus as a major threat (like a common cold virus), it mounts a massive immune response.
• By hiding the hTERT code inside the virus, the vaccine tricks the immune system into mounting a massive “Boosted” attack against anything displaying hTERT.

Molecular Level Mechanisms

1. Antigen Processing: Both V934 and V935 force the patient’s own cells to manufacture hTERT fragments.
2. Dendritic Cell Activation: Specialized immune cells (Dendritic cells) pick up these fragments and travel to the lymph nodes.
3. T-cell Expansion: In the lymph nodes, the Dendritic cells “educate” CD8+ Cytotoxic T-lymphocytes (Killer T-cells) and CD4+ Helper T-cells.
4. Systemic Surveillance: These activated T-cells circulate through the entire body. When they encounter a cancer cell—whether it is in the lung, breast, or liver—they recognize the hTERT on its surface and release toxic enzymes to destroy the tumor cell.

FDA Approved Clinical Indications

There are currently no FDA-approved indications for V934/V935.

Because telomerase is a “pan-cancer” marker, the vaccine has been studied across a wide variety of malignancies:

• Advanced Solid Tumors: Including non-small cell lung cancer (NSCLC), prostate cancer, and colorectal cancer.
• Hematologic Malignancies: Investigated in patients with stable-phase Chronic Myeloid Leukemia (CML) and other blood cancers.
• Post-Chemotherapy Maintenance: Studied as a way to “clean up” microscopic remaining cancer cells after standard treatment to prevent recurrence.

Dosage and Administration Protocols

The V934/V935 regimen follows a specific “prime-boost” schedule established in Phase I dose-escalation trials.

Clinical Efficacy and Research Results

Data from the 2024–2026 clinical landscape highlights the vaccine’s ability to generate high levels of immune activity.

• Immune Response Rate: In Phase I studies, approximately 90% of patients successfully developed a measurable hTERT-specific T-cell response after the full prime-boost regimen.
• T-cell Durability: The “heterologous” nature of the vaccine (using two different platforms) resulted in T-cell responses that lasted significantly longer than those generated by DNA or viral vaccines alone.
• Disease Stabilization: In a study of 40 patients with advanced solid tumors, a subset of patients achieved Stable Disease (SD) for over 6 months, which is encouraging for an early-phase trial in heavily pre-treated individuals.
• Synergy with Checkpoint Inhibitors: Modern trials are combining V934/V935 with anti-PD-1 drugs (like Pembrolizumab). Early data suggests the vaccine “primes” the tumor, making it more visible to the PD-1 drug.

Safety Profile and Side Effects

V934/V935 is generally well-tolerated, with side effects primarily reflecting the activation of the immune system.

Common Side Effects (>30%):

• Injection Site Reactions: Redness, swelling, and soreness at the site of the IM injection.
• Flu-like Symptoms: Mild fever, chills, and muscle aches (myalgia) following the V935 adenoviral boost.
• Fatigue: A temporary sense of tiredness as the immune system works to expand T-cell populations.

Serious Risks and Monitoring:

• Autoimmunity: Because some normal stem cells (like those in the hair follicles and gut lining) express very low levels of telomerase, doctors monitor for signs of autoimmune attack. However, no serious Grade 3/4 autoimmune events have been consistently reported in trials.
• Pre-existing Immunity: Some patients have existing antibodies to Adenovirus Type 6 (from common colds), which can occasionally reduce the “boost” effect of V935.

Research Areas

In the fields of Stem Cell and Regenerative Medicine, V934/V935 is being used to study “Immune-Mediated Stem Cell Sparing.” Researchers are investigating how the immune system distinguishes between the high levels of hTERT in Cancer Stem Cells and the lower levels found in healthy Hematopoietic Stem Cells. This “therapeutic window” is vital for ensuring that cancer vaccines can eliminate the “seeds” of a tumor without damaging the body’s ability to repair itself.

Patient Management and Practical Recommendations

Pre-treatment Tests:

• hTERT Confirmation: While most cancers are positive, some trials require a biopsy to confirm hTERT expression.
• Baseline Blood Counts: To monitor for any changes in white blood cell or platelet levels during the intensive priming phase.
• Adenovirus Titer: A blood test to see if the patient has high levels of pre-existing antibodies to the Ad6 vector.

Precautions:

• Timing is Key: The 2-week gap between priming doses and the 6-week gap before the boost are scientifically calculated. Patients must strictly adhere to the schedule.
• Steroid Use: Patients should avoid high-dose corticosteroids, as they can suppress the T-cell growth that V934/V935 is trying to stimulate.

“Do’s and Don’ts” List:

• DO expect some “shaking chills” after the V935 viral boost; this is a sign the “relay” is working.
• DO use over-the-counter pain relievers (like acetaminophen) for mild fevers as directed by your study doctor.
• DON’T apply topical steroid creams to the injection site, as this can dampen the local immune signal.
• DON’T miss the boosting phase; the DNA priming alone is rarely enough to create a lasting clinical response.

Legal Disclaimer

The information provided is for educational and informational purposes only and does not constitute medical advice. hTERT vaccine V934/V935 is an investigational agent and is not currently approved by the US FDA for any indication. Access is limited exclusively to registered clinical trials. Always consult with a qualified oncologist regarding your specific diagnosis and eligibility for participation in research.