Anktiva's New Bladder Cancer Approval Runs on Inference, and FDA Says That's the Point
FDA expanded Anktiva's use to BCG-unresponsive, high-grade papillary-only bladder cancer without a dedicated trial, leaning on earlier carcinoma in situ data and scientific similarities. The move sets a precedent developers of rare indications will study closely.
On October 14, the FDA expanded the approved use of Anktiva (nogapendekin alfa inbakicept-pmln) to include adults with high-grade papillary-only bladder cancer that has not spread into the bladder muscle and has not responded to BCG. What makes the decision unusual is what did not happen before it: no new dedicated trial for the papillary-only population. Instead, the agency built the approval out of evidence from the drug's earlier carcinoma in situ (CIS) program plus a scientific argument that the two forms of disease are close enough relatives to share a conclusion.
Anktiva is the first FDA-approved treatment specifically for patients with BCG-unresponsive, high-grade papillary-only disease. R. Angelo de Claro, MD, Director of FDA's Oncology Center of Excellence, said the review of similarities between these cancers allowed the agency to build on the CIS results and expand options for high-grade papillary tumors alone, and that the approach may help guide development of future treatments.
Why FDA said the two diseases travel together
The biological case rests on anatomy and behavior. In the bladder, CIS forms flat patches along the lining, while papillary tumors grow from the lining into the bladder as small finger-like projections. CIS is always high-grade; papillary tumors can be low- or high-grade. FDA stated that CIS and high-grade papillary tumors often occur together, can be difficult to distinguish under a microscope, and carry a high risk of returning or progressing when BCG stops working.
The evidence underneath: the CIS trial
The approval leans on trial NCT03022825 (QUILT-3.032), a single-arm, multicenter study that enrolled 88 adults for safety, of whom 77 were evaluable for efficacy, all with BCG-unresponsive high-risk non-muscle invasive bladder cancer with CIS with or without papillary tumors after transurethral resection. The complete response rate was 62% (95% CI: 51-73), with response defined by negative cystoscopy and urine cytology. Of patients achieving a complete response, 58% maintained it at least 12 months and 40% at least 24 months.
Anktiva was approved on April 22, 2024 for BCG-unresponsive non-muscle invasive bladder cancer with CIS with or without papillary tumors, after receiving breakthrough designation. The same regimen carries forward into the expanded use: Anktiva is given with BCG directly into the bladder through a catheter, once weekly for six weeks at 400 mcg, with a possible second six-week induction course if no complete response at month 3, maintenance doses at months 4, 7, 10, 13, and 19, optional additional doses at months 25, 31, and 37, and a maximum treatment duration of 37 months. Treatment stops if cancer persists after a second induction course, returns or progresses, or side effects become unacceptable.
The label carries a pointed warning: delaying surgery to remove all or part of the bladder can allow the cancer to spread to other parts of the body, which can be fatal. Common side effects include painful or frequent urination, urinary urgency, blood in urine, urinary tract infection, muscle or joint pain, chills, fever, and increased blood creatinine and potassium.
The alternative is surgery
The stakes are easiest to see against the landscape that exists when BCG fails. Radical cystectomy has been the standard guideline alternative for high-risk disease after BCG failure, and during the BCG supply shortage that began around 2019, when Merck became the sole US supplier of TICE BCG, guidance organizations told clinicians that high-risk patients unwilling to accept the oncologic risks of alternatives should be offered initial radical cystectomy. Against that backdrop, a drug option that spares the bladder carries real weight, even one approved on bridged evidence.
Mechanism and sponsorship
Nogapendekin alfa inbakicept-pmln is a mutated form of interleukin-15 (IL-15N72D), an IL-15 superagonist complex; IL-15-based superagonists can promote conversion of memory CD8+ T cells into innate-like effector cells with antitumor activity. BCG activates the immune system inside the bladder, and the combination pairs that local activation with the cytokine signal. The approval was granted to Altor BioScience, LLC, an indirect wholly-owned subsidiary of ImmunityBio, Inc. (IBRX); Altor was acquired by NantCell, a NantWorks company, in 2017.
A shortcut with conditions
FDA is working toward finalizing its draft guidance, "Bacillus Calmette-Guerin-Unresponsive Nonmuscle Invasive Bladder Cancer: Developing Drugs and Biological Products for Treatment," which is intended to include discussion of using evidence from CIS studies to support approval of treatments for BCG-unresponsive, high-grade papillary-only disease. That formalization, if finalized, would turn a one-off judgment into a template.
The inferential part is worth stating plainly: the CIS trial was not designed as a papillary-only trial, and this approval rests on reasoning across disease forms, not direct demonstration in the new population. That is the trade the agency made. The reward is an approved option, and a first one, for a patient group whose main alternative was surgical removal of the bladder. The cost is that the approval's strength is borrowed, and its durability will be judged by what happens in the patients who receive it. For developers in indications too small or slow to trial separately, the de Claro quote is the signal worth rereading: similarities between related conditions, carefully documented, may be allowed to carry part of the evidentiary load.