The FDA will not grant accelerated approval to Amgen’s experimental melanoma treatment talimogene laherparepvec, citing trial size, narrow data review and other approved melanoma treatments, according to briefing documents published by the regulator.

Amgen’s experimental injection, referred to by the shorthand T-Vec, is a modified herpes virus. It is injected into the cancer to jump-start an immunological response to help the body fight the disease.

The FDA’s Cellular, Tissue and Gene Therapies and Oncologic Drugs advisory committees are expected to meet Wednesday. The FDA released the joint report ahead of Wednesday’s discussion, when the committees will consider the drug as a standalone treatment.

Amgen’s Research and Development EVP Sean Harper told investors during last week’s earnings report that although monotherapy status will be important for specific patient groups, “the vast majority of the potential value of T-Vec lies in priming [the] immune system in combination with Type-1 inhibitors and other mechanisms that modulate the immune system.” Amgen and Merck inked an agreement last year to explore how T-Vec worked with Merck’s PD-1 inhibitor Keytruda (pembrolizumab).

The briefing documents indicate that Amgen got scooped somewhat by recently approved melanoma treatments, like Keytruda and Bristol-Myers Squibb’s Opdivo (nivolumab), as well as other drugs, like BMS’s Yervoy (ipilimumab), which was first approved in 2011. The documents show that these effective treatments were not available when Amgen kicked off testing in 2009. Reviewers wrote that the availability of these new drugs reduces the urgency associated with an accelerated approval designation for T-Vec. Accelerated approval can be granted if a medication fills a treatment gap.

The documents also show some wariness about the trials. Although an endpoint assessment committee evaluated complete response or partial response to the medication—the trial’s primary endpoints—investigators determined what patient data the committee reviewed, as opposed to providing data for all patients.

Although reviewers still characterized the data for these endpoints as robust, they questioned the meaningfulness of the results because the primary endpoint data were not affected by additional information such as if the cancer progressed after the study period or if patients developed new lesions. Overall survival data were not robust, in part because the 436-patient group was small.

Analysts declined to address the drug’s importance to the melanoma sector or for Amgen itself, but Amgen has not heavily promoted the drug as part of its pipeline. Instead, analysts have focused largely on Amgen’s heart-failure medication Corlanor (ivabradine), which was just approved, and cholesterol-lowering Repatha (evolocumab), which the FDA is expected to review by Aug. 27.