What is known about ADSTILADRIN (nadofaragene firadenovec‑vncg) intravesical therapy administered every three months for a 67‑year‑old woman with high‑risk BCG‑unresponsive non‑muscle‑invasive bladder cancer, including efficacy, safety, dosing, monitoring, and FDA regulatory status?

ADSTILADRIN for BCG-Unresponsive Bladder Cancer: Comprehensive Review

FDA Approval Status and Indication

ADSTILADRIN (nadofaragene firadenovec-vncg) received FDA approval on December 16,2022, and is currently an approved treatment option for high-risk BCG-unresponsive non-muscle invasive bladder cancer with carcinoma in situ (CIS), with or without papillary tumors. 1, 2, 3

• This represents the first FDA-approved adenoviral vector-based gene therapy and the first approved gene therapy for bladder cancer 2, 3
• The approval is specifically for adult patients who are ineligible for or decline radical cystectomy 1, 2

Mechanism of Action

ADSTILADRIN is a nonreplicating adenoviral vector that delivers human interferon alfa-2b (IFN-α2b) cDNA directly into bladder urothelial cells, producing local anticancer effects through immunostimulation, antiangiogenesis, and apoptosis. 4, 3, 5

• The gene therapy transfects urothelial cells to produce IFN-α2b locally within the bladder, avoiding systemic exposure 3, 5
• This mechanism provides both direct tumor cell killing and indirect immune-mediated antitumor activity 5

Dosing and Administration Schedule

The approved dosing regimen is 75 mL intravesical instillation (3 × 10¹¹ viral particles/mL) administered once every 3 months. 1, 4

Treatment Duration

• Initial treatment period: up to 12 months (4 doses total) 1
• Patients without high-grade recurrence may continue treatment every 3 months beyond 12 months 1, 6
• In the pivotal trial, 27% of patients received ≥5 instillations and 7.6% continued treatment for ≥57 months 6

Administration Details

• The product is shipped frozen at ≤-60°C and must be thawed to room temperature before use 1
• Once thawed, vials may be stored up to 24 hours at room temperature and up to 7 days refrigerated 1
• After drawing into syringes, the product may be stored up to 6 hours at room temperature 1
• Do not refreeze 1

Efficacy Data

Primary Efficacy Results (CS-003 Trial)

In the pivotal phase 3 trial of 98 evaluable patients with BCG-unresponsive NMIBC with CIS, ADSTILADRIN achieved a 51% complete response rate (95% CI: 41%-61%) at any time, with 46% of responders maintaining response for ≥12 months. 1, 2

• The median duration of response was 9.7 months (range: 3-52+ months) 1, 2
• At 3 months after initial treatment, 53.4% of patients with CIS achieved complete response 4
• Of those achieving complete response, 45.5% maintained it at 12 months 4

Long-Term Follow-Up Data (5-Year Results)

At 5 years of follow-up, ADSTILADRIN demonstrated durable bladder preservation in nearly half of patients, with cystectomy-free survival of 49% at 60 months. 6

• For patients with CIS: 43% cystectomy-free survival at 60 months 6
• For patients with high-grade Ta/T1 without CIS: 59% cystectomy-free survival at 60 months 6
• Overall survival at 60 months was 80% (76% in CIS cohort, 86% in Ta/T1 cohort) 6
• Only 5 patients (3.3%) experienced clinical progression to muscle-invasive disease over 5 years 6
• High-grade recurrence-free survival at 57 months: 13% for CIS cohort and 33% for Ta/T1 cohort 6

Comparative Context with Other Therapies

NCCN guidelines position ADSTILADRIN as a Category 2A recommendation (uniform consensus) for BCG-unresponsive high-risk NMIBC with CIS, with the same recommendation strength as pembrolizumab. 7

• For high-grade papillary Ta/T1 without CIS, ADSTILADRIN is Category 2B (some disagreement among panel members) 7
• The 24.3% 12-month complete response rate in the NCCN-cited data is lower than the FDA label due to different analysis populations 7

Safety Profile

Common Adverse Events

The most common adverse reactions are local bladder symptoms, with minimal systemic toxicity due to the intravesical route of administration. 7, 2, 4

Most frequent adverse events include:

• Instillation site discharge (24.3%) 7
• Fatigue (23.4%) 7
• Bladder spasm (17.8%) 7
• Urinary urgency (16.8%) 7
• Hematuria 2
• Chills and pyrexia 2
• Dysuria 2

Serious Adverse Events

Grade 3-4 treatment-emergent adverse events were rare, occurring in only 1% of patients, with urinary urgency being the most common. 7, 4

• Only 2 patients (1.3%) discontinued treatment due to drug-related adverse events 7
• No treatment-related deaths occurred 4
• Most adverse events were grades 1-2 7

Practical Management of Bladder Spasms

Rectal diazepam 10 mg pretreatment significantly reduces bladder spasms and medication leakage during instillation, improving treatment retention and potentially efficacy. 8

• Rectal diazepam reduced bladder spasm incidence by 24% absolute risk reduction (32% vs 56%) 8
• Medication retention failure decreased by 25% absolute risk reduction (4% vs 29%) 8
• Patients without medication leakage had lower 3-month recurrence rates (18% vs 38%), though not statistically significant 8
• Only one patient experienced fatigue attributable to rectal diazepam 8

Clinical Positioning and Guidelines

NCCN Guidelines (2024)

NCCN recommends ADSTILADRIN as an option for select patients with BCG-unresponsive or BCG-intolerant high-risk NMIBC, specifically mirroring the recommendations for pembrolizumab. 7

Specific recommendations:

• Category 2A (uniform consensus): BCG-unresponsive high-risk NMIBC with CIS (with or without papillary tumors) 7
• Category 2B (some disagreement): BCG-unresponsive high-risk NMIBC with high-grade papillary Ta/T1 only without CIS 7
• The panel intentionally mirrored recommendations for ADSTILADRIN and pembrolizumab because they felt the agents would be considered under similar circumstances with similar data 7

ESMO Guidelines (2022)

ESMO guidelines do not specifically mention ADSTILADRIN by name, as the guidelines predate FDA approval, but they emphasize that radical cystectomy should be offered to all patients with BCG-unresponsive disease due to high progression risk. 7

• Pembrolizumab is mentioned as an option for BCG-unresponsive disease in patients not fit for or refusing cystectomy (Level III, Grade C evidence) 7
• Thermo-chemotherapy can achieve 2-year disease-free survival in 47% of patients as an alternative 7

Treatment Hierarchy for BCG-Unresponsive Disease

Radical cystectomy remains the gold standard for BCG-unresponsive NMIBC and should be offered first to all surgical candidates, as it provides the best oncologic outcomes with long-term survival exceeding 90%. 9

When cystectomy is declined or patient is ineligible, bladder-sparing options include:

1. FDA-approved intravesical gene therapy: ADSTILADRIN (Category 2A for CIS) 7, 9
2. FDA-approved systemic immunotherapy: Pembrolizumab (Category 2A for CIS) 7, 9
3. Alternative intravesical chemotherapy: Sequential gemcitabine/docetaxel (1-year RFS 65%, 2-year RFS 52%) 9
4. Device-based therapy: Thermo-chemotherapy (2-year DFS 47%) 9

Monitoring and Surveillance

During Treatment

Cystoscopy and urinary cytology should be performed every 3 months during the first 2 years of treatment. 10

• Complete response is assessed at 3,6,9, and 12 months by cystoscopy and cytology 1
• Random bladder biopsy of five sites is conducted in patients remaining in complete response at month 12 1
• Upper tract imaging should be performed every 1-2 years for high-grade tumors 10

Response Assessment

Initial response evaluation occurs at 3 months after the first dose using cystoscopy and urine cytology. 10

• Low-grade (Ta) papillary disease is not considered a recurrence for purposes of evaluating complete response 1
• If disease persists or recurs at 3-month evaluation, strongly consider radical cystectomy as the preferred option 10

Critical Considerations for Your 67-Year-Old Patient

Patient Selection Criteria

ADSTILADRIN is specifically indicated for patients with BCG-unresponsive high-risk NMIBC with CIS, with or without papillary tumors, who are ineligible for or decline radical cystectomy. 1, 2

Key eligibility requirements from the pivotal trial:

• BCG-unresponsive disease defined as: persistent disease after adequate BCG, recurrence after initial tumor-free state, or T1 disease after single BCG induction 1
• Adequate BCG defined as: ≥5 of 6 doses of initial induction plus either ≥2 of 3 maintenance doses or ≥2 of 6 doses of second induction 1
• All resectable disease (Ta and T1 components) must be removed by TURBT prior to treatment 1
• Residual CIS not amenable to complete resection is allowed 1

Exclusion criteria:

• Extra-vesical disease (urethra, ureter, renal pelvis) 1
• Muscle-invasive (T2-T4) or metastatic urothelial carcinoma 1

Age Considerations

The median age in the pivotal trial was 70 years (range 44-89), with 32% of patients >75 years old, demonstrating safety and efficacy in older adults like your 67-year-old patient. 1

Important Caveats and Pitfalls

Delaying cystectomy in high-risk surgical candidates can result in substantial progression risk; therefore, cystectomy candidacy must be thoroughly assessed before committing to bladder-sparing therapy. 9

• Patients with low GFR, variant histology, and tumor size >3 cm have particularly poor outcomes without cystectomy 9
• High-risk features requiring early cystectomy consideration: high-grade T1 with concomitant CIS, lymphovascular invasion, prostatic urethral involvement, or variant histology 9
• Only 5 patients (3.3%) progressed to muscle-invasive disease over 5 years in the ADSTILADRIN trial, but this represents highly selected patients 6

The every-3-month dosing schedule is less intensive than other intravesical therapies but requires long-term commitment and regular surveillance. 7, 11

• This represents a significant quality-of-life advantage compared to weekly or monthly intravesical treatments 11
• However, patients must be willing and able to maintain quarterly cystoscopy surveillance 10

Practical Implementation

Successful ADSTILADRIN administration requires proper storage, handling, and instillation procedures, with consideration of bladder spasm prophylaxis. 1, 11, 8

• Consider rectal diazepam 10 mg pretreatment to reduce bladder spasms and improve medication retention 8
• Universal biosafety precautions should be followed for handling 1
• The product must be protected from light 1

Current Status and Future Directions

ADSTILADRIN is fully FDA-approved and commercially available, not investigational, representing an established treatment option for BCG-unresponsive NMIBC with CIS. 1, 2, 3

• The drug received FDA approval in December 2022 and has been in clinical use since then 2, 3
• Long-term data through 5 years demonstrates sustained bladder preservation in approximately half of patients 6
• Future research focuses on optimizing patient selection, disease prognostication, and potential combination strategies 5, 12

For your 67-year-old patient, ADSTILADRIN represents a reasonable bladder-sparing option if she has BCG-unresponsive CIS and either declines or is not a candidate for radical cystectomy, with the understanding that cystectomy remains the gold standard treatment with superior oncologic outcomes. 7, 9, 1