CDER Exclusivity Board: Can 3-Year Exclusivity Applied to a Prodrug Block 505(b)(2) NDA Approval for the Active Metabolite?

This is the second post in a series of posts dedicated to delving into and discussing various issues that arise with both 5-year New Chemical Entity (“NCE”) exclusivity and 3-year new clinical investigation exclusivity based on a small stack of Letter Decisions we obtained that were issued by the Exclusivity Board in the Center for Drug Evaluation and Research – the “CDER Exclusivity Board.” While our first post dealt with 5-year NCE exclusivity, this post (and the remainder of our posts in this series) will deal with 3-year new clinical investigation exclusivity.

First up is a relatively short, but nevertheless informative decision on the scope of two periods of 3-year exclusivity FDA granted in connection with the April 23, 2015 approval of Supplemental NDAs (“sNDAs”) for VALCYTE (valganciclovir HCl): one sNDA for VALCYTE Tablets (NDA 021304/S-011) and another for VALCYTE Oral Solution (NDA 022257/S-005). Both sNDAs were approved to “expand the Indications and Usage to include heart transplant patients from 1 month to 4 months of age and to extend the duration of dosing regimen from 100 days to 200 days post-transplantation for the prevention of CMV disease in pediatric kidney transplant patients 4 months to 16 years of age.”  The periods of 3-year exclusivity expired on April 23, 2018, and were coded in the Orange Book as “D-148” (“EXTENDED THE DURATION OF THE DOSING REGIMEN FROM 100 DAYS TO 200 DAYS POSTTRANSPLANTATION FOR THE PREVENTION OF CMV DISEASE IN PEDIATRIC KIDNEY TRANSPLANT”) and “NPP” (“NEW PATIENT POPULATION”).

Enter Exela Pharma Sciences, LLC’s (“Exela’s”) 505(b)(2) NDA 209347 for Ganciclovir Injection, 2mg/ml (500mg/250mL). FDA approved NDA 209347 on February 17, 2017 for the treatment of Cytomegalovirus (“CMV”) retinitis in immunocompromised adult patients, including patients with acquired immunodeficiency syndrome and for the prevention of CMV disease in adult transplant recipients at risk for CMV disease.

Knowing that approval date (and indication) kind of gives away FDA’s determination as to whether or not the scope of the later-expiring D-148 and NPP periods of 3-year exclusivity applicable to VALCYTE blocked the approval of NDA 209347. But that bottom line determination isn’t what we found particularly interesting about FDA’s February 16, 2017 CDER Exclusivity Board Letter Decision.

As the L-valyl ester of ganciclovir, valganciclovir HCl (VALCYTE) is actually a prodrug for ganciclovir. After oral administration, valganciclovir is rapidly converted to ganciclovir by intestinal and hepatic esterases.  Exela NDA 209347 is for the ganciclovir active metabolite, and not for the valganciclovir prodrug.  So, an issue for the CDER Exclusivity Board to consider was whether 3-year exclusivity granted pursuant to FDC Act § 505(c)(3)(E)(iv) for a prodrug could block approval of a 505(b)(2) NDA for the active metabolite, a different active ingredient.  Here’s how the CDER Exclusivity Board set up the issue under the statute:

The bar clause of section 505(c)(3)(E)(iv) [] describes 3-year exclusivity as blocking approval of a 505(b)(2) application for “a change approved in the supplement.” Although this language is not identical to the phrase “conditions of approval of such drug in the approved subsection (b) application” used in section 505(c)(3)(E)(iii), in determining the scope of exclusivity and which applications are barred, there are likewise two aspects of the inquiry.  One aspect of the inquiry focuses on the drug at issue.  Under FDA’s interpretation of section 505(c)(3)(E)(iv) of the FD&C Act, for a single-entity drug to be potentially barred by 3-year exclusivity for another single-entity drug, the drug must contain the same active moiety as the drug with 3-year exclusivity.  If the 505(b)(2) application for a single-entity drug seeks approval for the same drug (active moiety) to which exclusivity has attached, then the second aspect of the scope inquiry applies.  This aspect of the scope inquiry focuses on the exclusivity-protected change approved in the supplement. FDA examines the conditions of approval supported by the new clinical investigations (other than bioavailability studies) that were essential to approval of the supplement.  If the 505(b)(2) application for a single-entity drug is for the same drug for the same exclusivity-protected change approved in the supplement, it will be blocked.  However, 3-year exclusivity does not block a 505(b)(2) application for the same drug that does not seek approval for the exclusivity-protected change approved in the supplement.

Under the first aspect described above, FDA determined that VALCYTE and Exela’s drug product contain the same active moiety:

Although Valcyte and Exela’s Ganciclovir have different active ingredients—valganciclovir HCl and ganciclovir, respectively—the products have the same active moiety, ganciclovir. Because the two products at issue contain the same active moiety, Exela’s Ganciclovir could potentially be barred by Valcyte’s unexpired 3-year exclusivity.

Under the second aspect described above, FDA determined that despite containing the same active moiety, the scope of 3-year exclusivity applicable to VALCYTE did not touch on Exela’s product:

The Board must therefore consider whether the 505(b)(2) applicant is seeking approval for the exclusivity-protected changes approved in the supplements for Valcyte. The Board concludes that Exela is not seeking approval for the exclusivity-protected changes approved in the supplements.  Valcyte’s 3-year exclusivity relates to the new pediatric uses approved in the supplements.  Exela is seeking approval of Ganciclovir for only adult indications: the treatment of CMV retinitis in immunocompromised adult patients, including patients with AIDS, and prevention of CMV disease in adult transplant recipients at risk for CMV disease.  Exela is not seeking approval of Ganciclovir for any pediatric uses, and therefore, the conditions of approval for Ganciclovir are clearly outside the scope of Valcyte’s 3-year exclusivity.

The Letter Decision is helpful reminder that the scope of 3-year exclusivity extends to the active moiety for the approved conditions of use for which clinical investigations were conducted or sponsored by the NDA applicant and that were considered by FDA to be essential to the approval of the application (or supplement).

But wait . . . there’s more!

While clearly 3-year exclusivity does not block approval of a 505(b)(2) NDA for a drug product containing the same active moiety for a condition of use outside of the scope of that exclusivity, it does block approval of an ANDA for that drug for the same use. That is, unless such exclusivity-protected information is omitted from generic drug labeling, And provided FDA determines that the omission of such exclusivity-protected information does not make the proposed generic drug less safe or effective for the remaining conditions of use.

That brings us to the complex carve-out of the D-148 and NPP periods of 3-year exclusivity applicable to VALCYTE that FDA had to consider when approving ANDAs for generic versions of the drug product. According to “Model Labeling” drafted by FDA, the Agency recommended that ANDA applicants use in their proposed labeling the following dosage and administration table (focus on the pediatric dosage):

That table differs quite a bit from the same table in post-2015 labeling for VALCYTE:

And the table in the Model Labeling also differs a bit compared to the pre-2015 labeling for VALCYTE:

That being said, there seem to be some early shades in the Model Labeling of a so-called ANDA labeling “carve-in”/”carve-up.” That might make VALCYTE the precursor to the first true instance of an ANDA labeling “carve-in”/”carve-up”: FDA’s ruling on the approval of generic VELCADE (bortezomib) for Injection, 3.5 mg/vial (NDA 021602) (see our previous post here).