Melinta Therapeutics, LLC, Melinta Subsidiary Corp., Rempex Pharmaceuticals, Inc. v. Nexus Pharmaceuticals, Inc.

N OTE: This disposition is nonprecedential.
United States Court of Appeals
for the Federal Circuit
______________________
MELINTA THERAPEUTICS, LLC, MELINTA
SUBSIDIARY CORP., REMPEX
PHARMACEUTICALS, INC.,
Plaintiffs-Appellees
v.
NEXUS PHARMACEUTICALS, INC.,
Defendant-Appellant
______________________
2025-1281, 2025-1282
______________________
Appeals from the United States District Court for the
Northern District of Illinois in Nos. 1:21-cv-02636, 1:21-
cv-05995, Judge John F. Kness.
______________________
Decided: June 5, 2026
______________________
D AMIEN N. D OMBROWSKI, Venable LLP, New York,
NY, argued for plaintiffs-appellees. Also represented by
D OMINICK A. C ONDE, HA K UNG W ONG.
I MRON T. ALY , ArentFox Schiff LLP, Chicago, IL,
argued for defendant-appellant. Also represented by
HELEN H. J I, K EVIN MICHAEL N ELSON, M ATTHEW T HOMAS
WILKERSON.
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______________________
Before P ROST , BRYSON, and REYNA, Circuit Judges.
BRYSON, Circuit Judge.
This patent case arises under the infringement provi-
sion of the Hatch-Waxman Act, 35 U.S.C. § 271(e)(2).
Melinta Pharmaceuticals, Inc. (“Melinta”), brought this
action against Nexus Pharmaceuticals, Inc. (“Nexus”),
alleging that a Nexus generic antibiotic infringed two of
Melinta’s patents. The district court found that Nexus’s
generic product infringed Melinta’s patents and rejected
Nexus’s argument that the patents were invalid. We
affirm the district court’s decision as to the first of the two
patents and decline to reach the issues raised with respect
to the second.
I
The patents at issue in this case are Melinta’s U.S.
Patent Nos. 9,084,802 (“the ’802 patent”) and 9,278,105
(“the ’105 patent”). The two patents are directed to meth-
ods in which the addition of magnesium to an injectable
antibiotic formulation reduces hemolysis of red blood cells
(i.e., cell death) at the injection site.
For the ’802 patent, the claims at issue are:
1. A method of treating a bacterial infection in a
subject, wherein the method consists of:
administering a therapeutically effective
amount of a composition to a subject in
need thereof via an intravenous route of
administration,
wherein the composition consists of an
aqueous solution consisting of minocycline
or a salt thereof, a salt that comprises a
magnesium cation, and a base,
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wherein the molar ratio of magnesium cat-
ion to minocycline is greater than about
4:1, and
wherein the composition has a pH that is
no less than 4 and no greater than 6,
whereby injection site hemolysis of red
blood cells is reduced relative to intrave-
nous administration of a composition that
does not include magnesium.
7. The method of claim 1, wherein the composi-
tion has a pH between about 4.5 and 5.5.
18. The method of claim 1, wherein the total vol-
ume of the composition administered is less than
500 ml.
’802 patent col. 40, ll. 43–57; col. 41, ll. 1–2, ll. 23–24.
For the ’105 patent, the claim at issue is claim 27,
which depends from claim 1:
1. A method of treating a bacterial infection in a
subject, wherein the method comprises adminis-
tering a therapeutically effective amount of a
composition to a subject in need thereof via an in-
travenous route of administration, wherein the
composition comprises an aqueous solution of a 7-
dimethylamino-tetracycline antibiotic and a mag-
nesium cation, wherein the molar ratio of magne-
sium cation to 7-dimethylamino-tetracycline
antibiotic is greater than 3:1 and wherein the so-
lution does not comprise a pharmaceutically ac-
ceptable oil, has a pH greater than 4 and less than
7, and has an osmolality less than about 500
mOsmol/kg.
27. The method of claim 1, wherein the 7-
dimethylamino-tetracycline is minocycline.
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’105 patent col. 41, ll. 33–43; col. 42, ll. 47–48.
Melinta produces Minocin, “an aqueous solution con-
sisting of minocycline and magnesium that is used to
treat bacterial infections.” J.A. 1. Although Minocin first
entered the market in 1972, Melinta later reformulated
its product to address problems with the original formula-
tion. J.A. 6–7. The patents-in-suit relate to the reformu-
lated Minocin, which added magnesium, increased the pH
of the formulation, and decreased the size of the dose of
the injected formulation. J.A. 3, 8–10.
In October 2020, Nexus filed an Abbreviated New
Drug Application (“ANDA”) with the U.S. Food and Drug
Administration (“FDA”) seeking to develop a generic
version of Minocin. J.A. 11–12. Melinta sued Nexus,
alleging infringement of the ’105 and ’802 patents. J.A.
3–5.
After a four-day bench trial, the district court found
that Nexus’s generic product infringed all the asserted
claims. The court also found that Nexus failed to prove
the asserted claims were invalid for obviousness, indefi-
niteness, inadequate description, or lack of enablement.
J.A. 2. The district court permanently enjoined Nexus
from “manufacturing, using, offering for sale, or selling its
ANDA product” until the expiration of the ’802 and ’105
patents. J.A. 2, 128–29. Nexus took this appeal.
II
We review issues of claim construction de novo, except
that we review any factual findings underlying the court’s
construction for clear error. Teva Pharms. USA, Inc. v.
Sandoz, Inc., 574 U.S. 318, 333 (2015). “Whether a claim
satisfies the written description requirement is a question
of fact that, on appeal from a bench trial, we review for
clear error.” Alcon Rsch. Ltd. v. Barr Lab’ys, Inc., 745
F.3d 1180, 1190 (Fed. Cir. 2014) (citing Ariad Pharms.,
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Inc. v. Eli Lilly & Co., 598 F.3d 1336, 1351 (Fed. Cir.
2010)).
III
Nexus raises two issues with respect to the ’802 pa-
tent. First, Nexus challenges the district court’s construc-
tion of the terms “composition” and “administering” as
they relate to the use of a diluent in the claimed aqueous
solution. See ’802 patent col. 40, ll. 45–50. Nexus also
challenges the district court’s finding that the ’802 pa-
tent’s specification contained an adequate written de-
scription of the method of reducing “injection site
hemolysis” by comparing the claimed formulation contain-
ing magnesium with “a composition that does not include
magnesium.” See id. at col. 40, ll. 55–57; J.A. 121–24.
A
The terms “composition” and “administering” refer to
the process of intravenous administration of a pharma-
ceutical composition. In that process, a diluent is com-
monly added to the pharmaceutical ingredients to produce
a “reconstituted solution.” The reconstituted solution is
then further diluted to produce the “admixture” that is
injected into a patient’s vein. J.A. 29. The pharmaceuti-
cal ingredients must remain dissolved in the solution in
order to be administered intravenously. J.A. 9.
The district court construed the term “composition” in
the ’802 patent to refer to the three ingredients of minocy-
cline, magnesium, and a base, after those ingredients are
mixed together to make a solution and prior to the addi-
tion of the diluent that is required for the formulation to
be administered intravenously. J.A. 23. The court con-
strued the term “administering” to mean “to remedially
give the diluted composition to a patient via an intrave-
nous route.” J.A. 31.
Nexus argues that the reference in claim 1 to “admin-
istering . . . a composition” means that a diluent cannot be
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added to a composition before it is administered, because
claim 1 uses the closed term “consists of” (as opposed to
the open term “comprises”), and the ingredient list for the
claimed composition does not include a diluent. For that
reason, Nexus argues that its ANDA product, which
requires the addition of a diluent prior to administration,
cannot infringe the ’802 patent. Appellant’s Br. at 7–14.
Melinta, on the other hand, argues that the term “compo-
sition” refers to the “concentrated, reconstituted solution
prior to further dilution.” Appellees’ Br. at 10. According
to Melinta, a person of ordinary skill in the art would
understand that a diluent must be added to the composi-
tion before the composition is administered to a patient.
Id. at 10–18.
We agree with the district court’s construction of both
terms. Although the asserted claims of the ’802 patent do
not refer to a diluent, both the intrinsic and extrinsic
evidence support the district court’s construction. The
specification provides instructions for preparing an ad-
mixture by adding a diluent, which makes the solution
“ready for administration by or to the patient.” ’802
patent, col. 13, ll. 53–56. Three expert witnesses also
testified that a person of ordinary skill would understand
the need to dilute the composition prior to its administra-
tion. J.A. 29. Finally, the 2010 Minocin IV prescribing
information instructs that intravenous administration
should include reconstitution and then further dilution.
J.A. 2647. The 1973 prescribing information for Minocin
likewise instructs that “[t]he drug should be initially
dissolved and then further diluted to 500–1,000 cc” with
various solutions for intravenous administration. J.A.
2653.
Nexus’s proposed construction of the term “composi-
tion” suffers from an inconsistency. The district court
noted that “[t]o simultaneously hold, as [Nexus] argues,
that ‘composition’ includes a diluent but that ‘consists /
consisting of’ does not include a diluent is inconsistent at
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best, because both terms describe the same list of ingredi-
ents.”1 J.A. 25. A person of ordinary skill would know
that it is necessary to add a diluent to the composition
before administering it to the patient, as indicated in the
instructions provided with the prescribing information.
Because we agree with the district court’s construc-
tion of the terms “composition” and “administering,” we
reject Nexus’s challenge to the district court’s finding of
infringement, which was based on Nexus’s claim construc-
tion arguments.
B
The second issue raised by Nexus involves the limita-
tion in claim 1 of the ’802 patent related to the reduction
of injection site hemolysis. That limitation requires that
“injection site hemolysis of red blood cells is reduced
relative to intravenous administration of a composition
that does not include magnesium.” ’802 patent, col. 40, ll.
55–57. The question raised by that limitation is whether
the recited composition with magnesium cations results in
reduced hemolysis compared to a composition containing
no metal cations, or whether the composition with magne-
sium cations results in reduced hemolysis compared to a
composition containing other metal cations, such as
calcium cations.
1 At oral argument, Nexus confirmed that under its
construction, the term “administering” refers to adminis-
tering the composition without the diluent in it. Oral
Argument in Case No. 2025-1281, 2:40–51,
https://www.cafc.uscourts.gov/oral-arguments/25-1281_04
062026.mp3. Applying Nexus’s construction would mean
that Melinta’s product would also fall outside the claim,
because both Melinta’s product and Nexus’s ANDA prod-
uct require the use of a diluent. See J.A. 2483 (2021
Minocin IV), 2541 (ANDA product).
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Nexus contends that hemolysis must be reduced com-
pared to any other administration that does not include
magnesium. Under that construction, Nexus argues, the
asserted claims of the ’802 patent would be invalid for
lack of written description because the inventors failed to
show that they possessed a formulation that reduced
hemolysis compared to a minocycline formulation contain-
ing calcium cations. Appellant’s Br. at 14–18.
Melinta asserts that Nexus waived that argument be-
cause the argument appears in only a single sentence of
Nexus’s opening post-trial brief. Appellees’ Br. 22. If the
argument was not waived, Melinta contends that the
correct comparison is between the claimed composition
with magnesium and the same composition without
magnesium.
We reject Melinta’s contention that Nexus waived the
argument regarding the proper comparator. Nexus
presented that argument to the district court in its post-
trial brief, where it wrote, “In addition, the patent shows
hemolysis is not reduced compared to another formulation
‘without magnesium’ since calcium formulations had the
same effect.” J.A. 1114. Melinta responded to that argu-
ment at greater length, J.A. 1162, making it clear that
Melinta was aware of the argument. In addition, wit-
nesses at trial testified regarding the issue. See J.A. 1641
(Tr. 228:17–20); J.A. 1825 (Tr. 412:3–25). Under the
applicable Seventh Circuit standard, Nexus said enough
to preserve the issue for appellate review. See United
States v. Roque-Espinoza, 338 F.3d 724, 727 (7th Cir.
2003) (argument was not waived even if it was “woefully
underdeveloped”).2
2 Waiver is a procedural, non-patent-related issue
that is governed by regional circuit law. Riverwood Int’l
Corp. v. R.A. Jones & Co., 324 F.3d 1346, 1352 (Fed. Cir.
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On the merits, we hold that the district court did not
clearly err in finding the ’802 patent not invalid for lack of
written description. The most natural comparison for the
claim limitation “does not include magnesium” is between
a formulation that contains magnesium and one that is
the same as that formulation, except without magnesium.
In this case, the formulation that is otherwise the same
but lacks magnesium is the prior art product, which
contained minocycline without adding magnesium or any
other metal cation.
The specification encompasses the administration of
minocycline with various metal cations, but the focus
throughout is on the differences between formulations
with divalent metal cations—whether magnesium or
calcium—and those without. The specification begins
with a series of figures comparing formulations with such
cations against formulations lacking any metal cations.
’802 patent, Figs. 1–5; see also id. at col. 6, line 63,
through col.7, line 11. The specification also contains test
results showing the reduction in the incidence of hemoly-
sis in formulations containing magnesium or calcium
cations compared to formulations lacking such cations.
Id. at col. 7, ll. 32–37, col. 29, line 56, through col. 32, line
30. Although the claims of the ’802 patent are directed
only to magnesium, the specification indicates that the
inventors were aware that calcium could be used as the
cation in the formulation as well. Nothing in the specifi-
cation is directed to comparing the effect of magnesium
with that of calcium. Rather, the focus of the specification
is the reduction of hemolysis resulting from the inclusion
of magnesium or calcium, as compared to prior art formu-
lations, which did not include metal cations at all.
2003) (citation omitted). In this case, the applicable
regional circuit is the Seventh Circuit.
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To be sure, the district court’s construction of the
phrase “does not include magnesium” to mean simply
“does not include magnesium,” J.A. 40, does not expressly
exclude a formulation that lacks magnesium but includes
a different cation, such as calcium, in place of the absent
magnesium. However, interpreting the claim language to
compare a formulation containing magnesium with for-
mulations containing other divalent cations, such as
calcium, would be contrary to the overwhelming evidence
that the invention of the ’802 patent was directed to the
advantage of adding magnesium to a minocycline formu-
lation lacking divalent cations, and not to any advantage
magnesium might have compared to other metal cations.
All the in vitro hemolysis tests described in the speci-
fication of the ’802 patent involve comparisons between
solutions containing metal cations (either magnesium or
calcium) and solutions not containing metal cations. See
’802 patent, col. 6, line 62, through col. 7, line 15. Else-
where, the specification describes experiments showing
the effect of magnesium cations on hemolysis compared to
formulations containing no metal cations. See id. at col.
29, line 58, through col. 32, line 50. While the specifica-
tion describes experiments that tested minocycline-
magnesium and minocycline-calcium formulations, the
point of the experiments was to demonstrate that divalent
and trivalent cations reduce hemolysis, not to compare
the effect of magnesium cations with the effect of calcium
cations.
At the core of the patent’s invention was a formula-
tion that introduced magnesium to the existing minocy-
cline formulation. The 1973 Minocin product included a
warning against using a diluent containing calcium in its
intravenous administration instructions because “a pre-
cipitate may form.” J.A. 2653. The warning in the prior
art against administering minocycline with calcium
strongly suggests that the claim limitation was not meant
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to be addressed to a comparison between magnesium and
calcium with respect to their effect in reducing hemolysis.
Other evidence likewise indicates that the ’802 claims
were directed to a formulation without magnesium or any
other cations (such as in the original minocycline formula-
tion). David Griffith, one of the named inventors of the
’802 patent, testified at trial that the new formulation
was not “wildly hemolytic” compared to “minocycline in
saline without magnesium.” J.A. 1760 (Tr. 347:3–7); see
J.A. 1825 (Tr. 412:5–7) (“The study [was] designed entire-
ly to compare the divalent-cation formulations to the
original formulation of minocycline.”). His testimony at
trial aligns with statements made during the prosecution
of the application that the closest prior art was commer-
cially available intravenous minocycline without a multi-
valent cation, and that experimental comparisons were to
that product or minocycline without metal cations. See
U.S. Patent Application No. 14/204,881, Declaration of
David Griffith under 37 C.F.R. § 1.132 ¶¶ 4, 8 (Aug. 27,
2014) (discussing the closest prior art and experiments
“comparing the effects of high molar ratios of multivalent
cations with minocycline as compared to formulations
lacking multivalent cations”).
The district court found that a person of ordinary skill
in the art “would understand this data to show that
reduced incidence of injection site hemolysis occurred in a
solution containing minocycline and a metal cation.” J.A.
35 (citation omitted). The specification fully supports the
district court’s observation, as the specification states that
hemolysis of red blood cells was reduced in an in vitro
model formulated with divalent cations “compared to
minocycline solutions formulated without divalent cati-
ons.” ’802 patent, col. 31, ll. 14–17; col. 32, ll. 27–30
(other examples). Thus, it is clear that the inventors were
in possession of an invention that showed a minocycline
solution with magnesium reduced hemolysis “relative to
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intravenous administration of a composition that does not
include magnesium.” Id. at claim 1.
IV
In summary, we uphold the district court’s judgment
that the ’802 patent was infringed and is not invalid.
Because both the ’802 patent and the ’105 patent have the
same expiration date, and because counsel agreed that if
either patent is held not invalid, the district court’s find-
ing of infringement must be upheld, see Oral Arg. in Case
No. 2025-1281 at 17:45–18:15, 38:58–39:12, it is unneces-
sary for us to address the question of the validity of the
’105 patent.
AFFIRMED
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