v3.25.2
Secured and unsecured senior debt
 6 Months Ended
Jun. 30, 2025
Debt Disclosure [Abstract]  
Secured and unsecured senior debt SECURED AND UNSECURED SENIOR DEBTThe following table summarizes our outstanding indebtedness and respective principal payments remaining as of June 30, 2025 (dollars in thousands):
Stated 
Rate
Interest
Rate(1)
Maturity
Date(2)
Principal Payments Remaining for the Periods Ending December 31,
Unamortized
(Deferred
Financing
Cost),
(Discount)/
Premium
Debt
2025
2026
2027
2028
2029
Thereafter
Principal
Total
Secured note payable
Greater Boston(3)
SOFR+2.70%
7.16%
11/19/26
(3)
$—
$153,624
$—
$—
$—
$—
$153,624
$(124)
$153,500
Unsecured senior line of credit and
commercial paper program(4)
(4)
4.71
(4)
1/22/30
(4)
—
—
—
—
—
1,100,000
1,100,000
(2,007)
1,097,993
Unsecured senior notes payable
4.30%
4.50
1/15/26
—
300,000
—
—
—
—
300,000
(284)
299,716
Unsecured senior notes payable
3.80%
3.96
4/15/26
—
350,000
—
—
—
—
350,000
(408)
349,592
Unsecured senior notes payable
3.95%
4.13
1/15/27
—
—
350,000
—
—
—
350,000
(812)
349,188
Unsecured senior notes payable
3.95%
4.07
1/15/28
—
—
—
425,000
—
—
425,000
(1,100)
423,900
Unsecured senior notes payable
4.50%
4.60
7/30/29
—
—
—
—
300,000
—
300,000
(916)
299,084
Unsecured senior notes payable
2.75%
2.87
12/15/29
—
—
—
—
400,000
—
400,000
(1,860)
398,140
Unsecured senior notes payable
4.70%
4.81
7/1/30
—
—
—
—
—
450,000
450,000
(1,872)
448,128
Unsecured senior notes payable
4.90%
5.05
12/15/30
—
—
—
—
—
700,000
700,000
(4,339)
695,661
Unsecured senior notes payable
3.375%
3.48
8/15/31
—
—
—
—
—
750,000
750,000
(4,027)
745,973
Unsecured senior notes payable
2.00%
2.12
5/18/32
—
—
—
—
—
900,000
900,000
(6,506)
893,494
Unsecured senior notes payable
1.875%
1.97
2/1/33
—
—
—
—
—
1,000,000
1,000,000
(6,675)
993,325
Unsecured senior notes payable
2.95%
3.07
3/15/34
—
—
—
—
—
800,000
800,000
(6,857)
793,143
Unsecured senior notes payable
4.75%
4.88
4/15/35
—
—
—
—
—
500,000
500,000
(4,730)
495,270
Unsecured senior notes payable
5.50%
5.66
10/1/35
—
—
—
—
—
550,000
550,000
(6,624)
543,376
Unsecured senior notes payable
5.25%
5.38
5/15/36
—
—
—
—
—
400,000
400,000
(3,939)
396,061
Unsecured senior notes payable
4.85%
4.93
4/15/49
—
—
—
—
—
300,000
300,000
(2,814)
297,186
Unsecured senior notes payable
4.00%
3.91
2/1/50
—
—
—
—
—
700,000
700,000
9,916
709,916
Unsecured senior notes payable
3.00%
3.08
5/18/51
—
—
—
—
—
850,000
850,000
(11,034)
838,966
Unsecured senior notes payable
3.55%
3.63
3/15/52
—
—
—
—
—
1,000,000
1,000,000
(13,450)
986,550
Unsecured senior notes payable
5.15%
5.26
4/15/53
—
—
—
—
—
500,000
500,000
(7,482)
492,518
Unsecured senior notes payable
5.625%
5.71
5/15/54
—
—
—
—
—
600,000
600,000
(6,580)
593,420
Unsecured debt weighted-average interest
rate/subtotal
3.97
—
650,000
350,000
425,000
700,000
11,100,000
13,225,000
(84,400)
13,140,600
Weighted-average interest rate/total
4.01%
$—
$803,624
$350,000
$425,000
$700,000
$11,100,000
$13,378,624
$(84,524)
$13,294,100
(1)Represents the weighted-average interest rate as of the end of the applicable period, including amortization of loan fees, amortization of debt premiums (discounts), and other bank fees.
(2)Reflects any extension options that we control.
(3)Represents a secured construction loan held by our consolidated real estate joint venture for 99 Coolidge Avenue, where we have a 76.9% interest. As of June 30, 2025, this joint venture has $41.7 million available under existing lender
commitments. We expect to repay the entire $153.5 million balance in August 2025.
(4)Refer to “$5.0 billion unsecured senior line of credit” and “$2.5 billion commercial paper program” on the following page.
The following table summarizes our secured and unsecured senior debt and amounts outstanding under our unsecured senior
line of credit and commercial paper program as of June 30, 2025 (dollars in thousands):
Fixed-Rate
Debt
Variable-Rate
Debt
Weighted-Average
Interest
Remaining
Term
(in years)
Total
Percentage
Rate(1)
Secured note payable
$—
$153,500
$153,500
1.2%
7.16%
1.4
Unsecured senior notes payable
12,042,607
—
12,042,607
90.5
3.90
12.8
Unsecured senior line of credit
and commercial paper program
—
1,097,993
1,097,993
(2)
8.3
4.71
(2)
4.6
(3)
Total/weighted average
$12,042,607
$1,251,493
$13,294,100
100.0%
4.01%
12.0
(3)
Percentage of total debt
90.6%
9.4%
100%
(1)Represents the weighted-average interest rate as of the end of the applicable period, including expense/income related to the amortization of loan fees, amortization of
debt premiums (discounts), and other bank fees.
(2)As of June 30, 2025, we had no outstanding balance on our unsecured senior line of credit and $1.1 billion of commercial paper notes outstanding.
(3)We calculate the weighted-average remaining term of our commercial paper notes by using the maturity date of our unsecured senior line of credit. Using the maturity
date of our outstanding commercial paper notes, the consolidated weighted-average maturity of our debt is 11.6 years. The commercial paper notes sold during the six
months ended June 30, 2025 were issued at a weighted-average yield to maturity of 4.67% and had a weighted-average maturity term of 16 days.
Issuance and repayment of unsecured senior notes payable
In February 2025, we issued $550.0 million of unsecured senior notes payable, due 2035, with an interest rate of 5.50%.
In April 2025, we repaid our 3.45% unsecured senior notes payable aggregating $600.0 million upon their maturity, using 
proceeds from our February 2025 unsecured senior notes payable offering, with no gain or loss incurred in connection with this
repayment.
$5.0 billion unsecured senior line of credit
As of June 30, 2025, our unsecured senior line of credit, which matures in 2030, including extension options under our control, 
had aggregate commitments of $5.0 billion and bore an interest rate of SOFR plus 0.855%. In addition to the cost of borrowing, the
unsecured senior line of credit is subject to an annual facility fee of 0.145% based on the aggregate commitments outstanding. Based
upon our ability to achieve certain annual sustainability metrics, the interest rate and facility fee rate are also subject to upward or
downward adjustments of up to four basis points with respect to the interest rate and up to one basis point with respect to the facility fee
rate.
Based on certain sustainability metrics achieved in accordance with the terms of our unsecured senior line of credit
agreement, the borrowing rate was reduced for a one-year period by two basis points to SOFR plus 0.855%, from SOFR plus 0.875%,
and the facility fee was reduced by 0.5 basis point to 0.145% from 0.15%. As of June 30, 2025, we had no outstanding balance on our
unsecured line of credit.
$2.5 billion commercial paper program
Our commercial paper program provides us with the ability to issue up to $2.5 billion of commercial paper notes that bear
interest at short-term fixed rates with a maturity of generally 30 days or less and a maximum maturity of 397 days from the date of
issuance. Our commercial paper program is backed by our unsecured senior line of credit, and at all times we expect to retain a
minimum undrawn amount of borrowing capacity under our unsecured senior line of credit equal to any outstanding notes issued under
our commercial paper program. We use the net proceeds from the issuances of the notes for general working capital and other general
corporate purposes. General corporate purposes may include, but are not limited to, the repayment of other debt and selective
development, redevelopment, or acquisition of properties. During the six months ended June 30, 2025, the commercial paper notes
were issued at a weighted-average yield to maturity of 4.67% and had a weighted-average maturity term of 16 days. As of June 30,
2025, we had a $1.1 billion outstanding balance on our commercial paper program.
Interest expense
The following table summarizes interest expense for the three and six months ended June 30, 2025 and 2024 (in thousands):
Three Months Ended June 30,
Six Months Ended June 30,
2025
2024
2025
2024
Interest incurred
$137,719
$126,828
$268,660
$249,508
Capitalized interest
(82,423)
(81,039)
(162,488)
(162,879)
Interest expense
$55,296
$45,789
$106,172
$86,629